您可以创建一个全局变量loop_active，初始设置为False，然后单击set_breaks函数末尾的第一个按钮，使其触发一个单独的函数，该函数控制1秒循环，但仅当loop_active设置为false时，否则它将只执行常规检查。
在某种程度上，它是评论中建议的一种组合。更多细节请参见内联注解。
例如：

from tkinter import *
from tkinter import ttk
from datetime import datetime

root = Tk()

root.title("Fusion Calculator")
root.geometry("700x400")
root.resizable(0, 0)

scheduler_frame = LabelFrame(root, text='Scheduler')
scheduler_frame.pack(fill=X)

scheduler_top_frame = Frame(scheduler_frame)
scheduler_top_frame.pack(fill=X)

hours_label = Label(scheduler_top_frame, text="HH")
hours_label.grid(row=0, column=1, padx=10)

minutes_label = Label(scheduler_top_frame, text="MM")
minutes_label.grid(row=0, column=2, padx=10)

seconds_label = Label(scheduler_top_frame, text="SS")
seconds_label.grid(row=0, column=3, padx=10)

first_break_label = Label(scheduler_top_frame, text="1st Break:")
first_break_label.grid(row=1, column=0, pady=5)

second_break_label = Label(scheduler_top_frame, text="2nd Break:")
second_break_label.grid(row=2, column=0, pady=5)

meal_break_label = Label(scheduler_top_frame, text="Meal Break:")
meal_break_label.grid(row=3, column=0, pady=5)

logout_label = Label(scheduler_top_frame, text="Logout:")
logout_label.grid(row=4, column=0, pady=5)

hour_time_values = ('00', '01', '02', '03', '04', '05', '06', '07', '08', '09',
                    '10', '11', '12', '13', '14', '15', '16', '17', '18', '19',
                    '20', '21', '22', '23')

other_time_values = ('00', '01', '02', '03', '04', '05', '06', '07', '08',
                     '09', '10', '11', '12', '13', '14', '15', '16', '17',
                     '18', '19', '20', '21', '22', '23', '24', '25', '26',
                     '27', '28', '29', '30', '31', '32', '33', '34', '35',
                     '36', '37', '38', '39', '40', '41', '42', '43', '44',
                     '45', '46', '47', '48', '49', '50', '51', '52', '53',
                     '54', '55', '56', '57', '58', '59')

first_break_hour_value = StringVar()
first_break_hour_drop = ttk.Combobox(scheduler_top_frame,
                                     width=2,
                                     textvariable=first_break_hour_value)
first_break_hour_drop['values'] = hour_time_values
first_break_hour_drop.grid(row=1, column=1)
first_break_hour_drop.current(0)

first_break_minute_value = StringVar()
first_break_minute_drop = ttk.Combobox(scheduler_top_frame,
                                       width=2,
                                       textvariable=first_break_minute_value)
first_break_minute_drop['values'] = other_time_values
first_break_minute_drop.grid(row=1, column=2)
first_break_minute_drop.current(0)

first_break_second_value = StringVar()
first_break_second_drop = ttk.Combobox(scheduler_top_frame,
                                       width=2,
                                       textvariable=first_break_second_value)
first_break_second_drop['values'] = other_time_values
first_break_second_drop.grid(row=1, column=3)
first_break_second_drop.current(0)

second_break_hour_value = StringVar()
second_break_hour_drop = ttk.Combobox(scheduler_top_frame,
                                      width=2,
                                      textvariable=second_break_hour_value)
second_break_hour_drop['values'] = hour_time_values
second_break_hour_drop.grid(row=2, column=1)
second_break_hour_drop.current(0)

second_break_minute_value = StringVar()
second_break_minute_drop = ttk.Combobox(scheduler_top_frame,
                                        width=2,
                                        textvariable=second_break_minute_value)
second_break_minute_drop['values'] = other_time_values
second_break_minute_drop.grid(row=2, column=2)
second_break_minute_drop.current(0)

second_break_second_value = StringVar()
second_break_second_drop = ttk.Combobox(scheduler_top_frame,
                                        width=2,
                                        textvariable=second_break_second_value)
second_break_second_drop['values'] = other_time_values
second_break_second_drop.grid(row=2, column=3)
second_break_second_drop.current(0)

meal_break_hour_value = StringVar()
meal_break_hour_drop = ttk.Combobox(scheduler_top_frame,
                                    width=2,
                                    textvariable=meal_break_hour_value)
meal_break_hour_drop['values'] = hour_time_values
meal_break_hour_drop.grid(row=3, column=1)
meal_break_hour_drop.current(0)

meal_break_minute_value = StringVar()
meal_break_minute_drop = ttk.Combobox(scheduler_top_frame,
                                      width=2,
                                      textvariable=meal_break_minute_value)
meal_break_minute_drop['values'] = other_time_values
meal_break_minute_drop.grid(row=3, column=2)
meal_break_minute_drop.current(0)

meal_break_second_value = StringVar()
meal_break_second_drop = ttk.Combobox(scheduler_top_frame,
                                      width=2,
                                      textvariable=meal_break_second_value)
meal_break_second_drop['values'] = other_time_values
meal_break_second_drop.grid(row=3, column=3)
meal_break_second_drop.current(0)

logout_hour_value = StringVar()
logout_hour_drop = ttk.Combobox(scheduler_top_frame,
                                width=2,
                                textvariable=logout_hour_value)
logout_hour_drop['values'] = hour_time_values
logout_hour_drop.grid(row=4, column=1)
logout_hour_drop.current(0)

logout_minute_value = StringVar()
logout_minute_drop = ttk.Combobox(scheduler_top_frame,
                                  width=2,
                                  textvariable=logout_minute_value)
logout_minute_drop['values'] = other_time_values
logout_minute_drop.grid(row=4, column=2)
logout_minute_drop.current(0)

logout_second_value = StringVar()
logout_second_drop = ttk.Combobox(scheduler_top_frame,
                                  width=2,
                                  textvariable=logout_second_value)
logout_second_drop['values'] = other_time_values
logout_second_drop.grid(row=4, column=3)
logout_second_drop.current(0)

loop_active = False  # global variable set to false

def check_breaks():   # new loop function that runs set_breaks and reschedules
    set_breaks()      # for 1 second later.
    root.after(1000, check_breaks)

def set_breaks():
    check_break = datetime.now().strftime("%H:%M:%S")

    first_break_time = f'{first_break_hour_value.get()}:{first_break_minute_value.get()}:{first_break_second_value.get()}'

    second_break_time = f'{second_break_hour_value.get()}:{second_break_minute_value.get()}:{second_break_second_value.get()}'

    meal_break_time = f'{meal_break_hour_value.get()}:{meal_break_minute_value.get()}:{meal_break_second_value.get()}'

    logout_time = f'{logout_hour_value.get()}:{logout_minute_value.get()}:{logout_second_value.get()}'

    if check_break == first_break_time:
        popup_first_break = Toplevel(root)
        popup_first_break.title('Official Break')
        popup_first_break_title_bar = Label(popup_first_break, text='OFFICIAL BREAK', fg='Red')
        popup_first_break_title_bar.pack()
        print('Working')
    elif check_break == second_break_time:
        popup_second_break = Toplevel(root)
        popup_second_break.title('Official Break 2')
        popup_second_break_title_bar = Label(popup_second_break, text='OFFICIAL BREAK 2', fg='Red')
        popup_second_break_title_bar.pack()
        print('Working')
    elif check_break == meal_break_time:
        popup_meal_break = Toplevel(root)
        popup_meal_break.title('Official Break')
        popup_meal_break_title_bar = Label(popup_meal_break, text='MEAL BREAK', fg='Red')
        popup_meal_break_title_bar.pack()
        print('Working')
    elif check_break == logout_time:
        popup_logout = Toplevel(root)
        popup_logout.title('Official Break')
        popup_logout_title_bar = Label(popup_logout, text='LOGOUT', fg='Red')
        popup_logout_title_bar.pack()
        print('Working')
    else:
        print(check_break)
    global loop_active
    if not loop_active:   #  This will only run when loop_active is false
        loop_active = True   # Set loop_active to True so it doesn't run again
        check_breaks()       

set_breaks_button = Button(scheduler_top_frame,
                           text='Set',
                           command=set_breaks)
set_breaks_button.grid(row=5, column=3)

root.mainloop()