>>7705644
thinking a lot about doing stuff tricks your brain into thinking you've already done it, so the motivation and energy to actually do it gets used up. try not to think too hard about it, save the energy when you are free to actually draw.
drawing takes a lot of brainpower and many people need to be in a good mood to draw too, so it's hard to do when tired. schedule your drawing time when you're not tired.
prepare your desk and materials so there is less friction to get started.

set sketchbook/tablet and references/study materials to draw at your desk ready to go
go to bed 1 hour early, wake up 1 hour early
sit at desk first thing in the morning and draw when you aren't tired and before you can overthink it. drink a cup of coffee or tea if you want to, as caffeine can help you focus and set new habits.