I had a temporary roommate that studied cognitive science for his PhD, and I saw him using Habitica one day, so I asked him about it. It is a gamified app that helps people form, keep, or break habits, and it has worked excellently for me for the past 5 months.
I am the type of person who always meets all of my deadlines, but who puts things off until those deadlines. That means that I was good at school since there were things like weekly assignments that were assessed for points. However, it also means that it has been difficult for me to form good habits (eg, writing more or ending each day having responded to all emails) or to break bad habits (eg, not getting enough sleep) since there isn't a clear deadline and it's easy to put off.
Habitica turns your habits into a game. You have a set of dailies -- tasks that you want to do every day -- and if you do your dailies, you get experience points and gold, and if you miss your dailies, you lose health. You can also have positive and negative habits that you might be able to do multiple times per day (eg, wasting time on YouTube or drinking a lot of water). I haven't found this to be an effective way to establish positive habits, but I have found it extremely effective in eliminating negative habits when it's a habit that I actually want to eliminate.
Part of the reason that it's effective is because the brain has different parts, and our higher order thinking skills (eg, the habits we want to form, the goals that we have) are weaker in some ways than the short-term "oh, I'll just watch one more episode" part of our brain (often called the lizard brain). Habitica lets you create a concrete set of penalties and rewards for the higher order things which lets you use your short term thinking to your advantage.
Using Habitica is free, but I have started to pay for it anyways because it has had such an impact on me and I want to support the developers. It has helped me get more sleep, be more productive and intentional with my time, write more, be more responsive to emails, and more. If you are the type of person who is motivated by deadlines or game-style rewards and you want to form or break habits, check out Habitica. If you find it helpful, let me know!