The best time to start was 7 days ago, the second best time to start is now.
I struggle with this as well. If the step is too big I get overwhelmed and procrastinate the task untll panic sets in and fuels me with adrenaline.
Take a small step towards it without the intention to finish. Put the book out then do something else. Have the intention of just reading for 5 minutes then stop. Allow yourself to be satisfied in taking a step towards the big task.
Failing an exam you didn’t study for us not a failure of character. It’s not your fault, and it is not worth valuing higher than your life.
Depression is telling you that you put too much weight on yourself. Do your best and that is already 100% of what you can give right now, and that is OK.