Teaching 40 teenagers a day and coming home empty

I have taught for 14 years. I used to love it. Now by the last period I am counting the minutes, and when I get home I sit on the sofa in my work saree for an hour before I can move. It is not the children. They are the same as they always were, loud and mostly sweet. It is the meetings, the parents messaging at 10 pm, the syllabus that changes every year, and the feeling that nobody in the management has any idea what a classroom is like. I cannot leave. The salary, the pension, my age. Teachers here, how do you keep going when the job that gave you purpose starts taking it away?