When you're depressed you don't think very rationally, you find ways to put your self down and make excuses, then hate yourself for avoiding things because of excuses.

Make sure to pay attention to when your body is doing and try to detach it from your decision making as much as possible.

If you start to get dissapointed at yourself for not doing something, being sad, and other negative things that depression causes, then you should remember that is all in your past and you can't change it. Worrying about things you can't change or is out of your control only causes unnecessary stress, it only hurts you rather then help. So when you realized you can't change the past, you can focus doing your best in the now, this will help your motivation to do more things, and practicing this is key to beating depression.

One method I do is to only think of things that help my situation and to avoid stray thoughts to focus on the goal you're trying to do and break down all the steps of reaching that goal.

Then just start working on each step for progress, try to immediately do that step as soon as you think of it, before you overthink it and convince yourself to use an excuse.

Doing this method of getting things done and keeping yourself busy will let you see things in an optimistic way, lowering your stress by not thinking of the past, and slowly will help you beat depression.

I don't actually have any qualifications to say this, but these methods help reduce stress and help your motivation and recognize when depression is causing you to think irrationally. If your focus starts to think about you think you're a terrible person, this is the depression.

Remember that while you can't control what thoughts come up in your brain, you choose what thoughts you develop. If a negative thought about you comes up, that's fine, you can just not develop that thought and let it fade away. Another method I've heard is to tell yourself "cancel" when you think these negative thoughts, and if they keep popping up in your thoughts to just keep telling yourself "cancel" as if you're choosing to throw this idea out. Say it enough until it drowns out the thought.