Another thing: There’s a difference between motivation and drive. Motivation comes in all kinds of forms, drive comes 100% from within.
You seem to be very driven to succeed, whatever that means for you, and meditation and other habits are tools you’ve picked up to support yourself in that drive. You do what it takes. You don’t need motivation to do those things because you have decided for yourself that they are going to serve you.
Is this is what you mean with successful people doing “what they don’t feel like doing”? The thing is, they’ve accepted that doing those things is just part of what they’re doing on the whole.
Some people don’t have that. They’ve got stuff to work out. Maybe they don’t even know they have stuff to work out. Either way, “getting better at mindfulness” sounds like a misguided approach to it, even dangerous. You see the benefits for yourself, or you don’t. If you do, you make it work. If you don’t…you don’t.