Overworked, tired and fucked.

I have been so busy at work. My supervisor is still on leave and I am buried in tons of work. My desk is filled with papers that all needs my immediate attention. And best of all I'm having to deal with issues I have not dealed with in my stint before.
Time flies. I reach office early and leave late. First to arrive and literally last to leave. My replacement is here and I am STILL so busy. I have to teach him everything in a couple of days and make sure my work gets done too. I am so tired. I OT every single day.
I need to remain positive and see the forest for the trees. I can do this WELL. I have to double my work rate and focus. How to work in a office where even after I write down every single step to take and explain the process, people still manage to make the mistakes? Is this a form of poor leadership or poor surbordinates? Seems like I have to run and supervise everything.
I must persevere. There must be a silver lining somewhere. Nothing shall affect me.