Discipline is about preparing for whatever is coming and whatever might come. It means practicing sticking techniques, so you can drum faster, or learning new presentation techniques. The goal isn't just to be able to execute well, but so you can respond with skill even if something unexpected happens. A prime example in music is hearing something in your head. Discipline means gathering techniques and honing skills so that when music presents itself, you are able to play it at the moment. This is the heart and soul of improvisation.
There is no mental exercise, no dietary change or miracle drug, no device which will give you discipline. Before those could even work, you would have to decide to let them work. There is one small trick: When you decide, phrase it to be positive, and current.
Example: I eat a low carb, high vegetable, quality protein diet. And not, say "I'll start a better diet tomorrow" or "I'll stop eating so much pasta"
The physical process of learning is rooted in neural pathways becoming more efficient, a process which entails physical changes in your brains and body. These don't happen instantly, or even quickly, but over hours and days. Practice must concentrate on reinforcing correct action. Time spent doing things badly for the sake of "putting the hours in" might actually be setting you back, because you are reinforcing bad habits.
Our habits are driven by dopamine, which drives us towards previous rewarding behavior, such as tasty snacks, or neat social media sites. The problem is that it doesn't know when restraint is a good idea. It's important to find a positive reward for getting away from those fun things which are costly in excess. This paragraph is careful and not bold. This reflects the trickiness of dopamine and neurophysiology in general