There is a guy from Stanford, BJ Fogg is the name IIRC, who does a course "Simple Habits". It's like, commit to doing 1 pushup for 5 days first thing in the morning. It is supposed to lead to forming long-term bigger habits, but I'm personally not convinced. Anyways, check him out.

Interesting, thanks. Still, it takes at least a bit of initial grit to do that one pushup - especially every day.

You need to get the ball moving with following your own instructions. The first tasks don't have to be useful or related, just doable. Eg force yourself to blink. Then raise one arm. Then stand up. Now you are half way to doing the pushup. Ignore the silliness of it all, and keep going. With each progressively harder step, you gain more momentum and more energy to take bigger steps.

If we are talking depression: try getting more veggies, try going for a walk outside. Small steps. Try changing your surrounding a bit. Then seek medical support ? And don't blame yourself.

Start by making your bed when you get up, because it's something easy that naturally belongs at that time, and gives you immediate visual feedback in the form of a nicer looking room.

But isn't the visual feedback counterproductive? I think grit means repeatedly doing it despite not having that immediate feedback. At least, that's the kind of habits I think people have a real problem sustaining.

I do make my bed every day, although not in the morning - I prefer to unmake it so it can receive sunlight. But I don't think it takes any willpower, since I find it a pleasant activity.