If you want to get good at something, you have to understand that interest will wane and fade. The only path to mastery, is one of sheer dedication.
Interest is a good way to get into a good habit, but you'll quickly realize it's not enough. You need to have the willpower to never break your habits.
Also, don't set high targets for your habits. Set them as low as possible. If you're interested in drawing, a good habit is to draw at least a single line per day. If you're feeling motivated, you'll most certainly draw more. Even if you're low on time, you must draw that single line no matter what.
The moment you break the habit, is the moment you've accepted defeat.