To add to Dheepa's point on discipline, developing routines and finding methods that work for you is a god send. I have really severe ADHD and depression so getting anything done (including things I enjoy) is a daily battle, and I've had to develop thorough routines to make sure I keep moving.
One thing that has been especially helpful is the idea of non-zero days. When things are feeling especially dire and hard, I try to make sure I have a minimum I do whether that be in terms of life admin or school work or some project I'm working on. If I can get 15 minutes done for the thing I'm working towards, even if I wanted or expected to do an hour, that day wasn't a waste and I am still making progress. 15 minutes is always better than 0, and I usually realise by the time the 15 minutes are over that I can do a bit more, or I can take a break and do another 15 minutes and then another. And on days where you really end up doing nothing, being kind to yourself and not beating yourself up over it is probably the best thing you can do. Self-cruelty helps nothing and only perpetuates a cycle of shame and procrastination.
Scheduling is also great. Blocking out specific chunks of time to do something and making yourself stick to it consistently helps you get into the headspace for that thing a lot faster than if you wait for the urge to strike you. To do lists are also very satisfying to cross off, especially if you break every single task into itty bitty chunks
. I also love the pomodoro method when it comes to actually working. 20 minutes on, 5 minutes off makes studying feel manageable, but then you look up and its been 4 hours and you've actually finished a lot of work.
Also, actually managing your stress levels is key. Meditation, exercise, creative hobbies, getting out into nature, eating right, are all very very important and I think that when things pile up people let them fall by the wayside because they think they don't have time or energy for them, when in fact they should cling to them more than ever.
These are just some of the things that work for me. As Dheepa said, you have to find what works for you. I hope it helps!