[ApolloRising]

This seems to help quite a few people a lot: http://www.habitbull.com/

It gives you a bit of a dopamine hit every time you check the box and really helps build good habits over time. The system is remarkably flexible for different kinds of habits.

(I am not the developer, just a happy customer)

One last thing, the best thing that seems to make a difference is to schedule your day hourly and maintain a rigid sleep/wake/exercise/eating schedule. Don't skip any of these and things will get better.

Mindfulness also seems to help but only if you practice it regularly, for ADHD folks that may mean scheduling a class and going to it every week to have the enforced practice.

Lastly, there is no quick fix, you are already motivated to get better since you asked the question; you now have to be motivated to be consistent and not let small failures make you give up.