How do you "stay disciplined" to brush your teeth every day? Chances are you just do it without thinking much about it. You don't hem and haw and read a bunch of motivational memes to gather up the willpower to brush your teeth. It's just something you automatically do.
I highly recommend the book Atomic Habits for advice about how to build up habits. The main key is to start small. If you want to get in shape, you're not going to start out working out for 90 minutes every day. You start with 5 minutes or something so easy that you can't not do it. Then you keep doing it until it becomes automatic and build from there.