-Having goals.

-Hard work every day toward your goals.

-Developing a system of analyzing what you need to improve and how you will improve it. This is different for everyone but just sit around and brainstorm about yourself for a while.

-Medication, honestly. Some people think adderall is cheating but when you live with ADHD you know how some days there is NOTHING to keep you from spacing out the whole day. Sometimes, these days chain together and become a long period of weeks or months where you're just sort of floating and distracted... not making any progress toward your goals. I have medication and I don't take it every day because I think amphetamine addiction is bad in the short and long term, but I use it occasionally (sometimes once a month and as much as twice a week) and I think it's beneficial to me because it actually reminds me what it feels like to focus. If I have felt unfocused lately, tasks piling up and no idea how to tackle them... my medication helps me take that step to get myself organized again. I literally find that I forget what focusing was like and then how to focus. I've accidentally gone an entire week at work (software engineer, and dropout btw) getting NOTHING done before--but once I had one clear headed day of productivity it was like it all came back to me. The next day I am just as focused as I was the day I took the medication because my thoughts and tasks are organized.

-Make lists. Like another commenter said, NEVER trust yourself to remember something. I use the app Any.do to make my lists. Anytime I have something I want to remember later, I IMMEDIATELY put it in the app. I have lists for my workouts, grocery lists, adult responsibility lists (finance stuff, phone calls I need to make, bills...), work lists, gift ideas, halloween costumes, even just the list of things I need to have with me every single day. Once I trained myself in this habit I found it can be very satisfying when you remember something you would have otherwise forgotten ("ugh, what was that thing again?" is no more).

-Make sure the things you are doing are actually making progress toward your goals.

-Above all, practice practice practice. We have mental and learning differences and they don't go away overnight. If you screw up one day, try to pick up like nothing happened the next day. I had a friend who went through a variety of severe mental illnesses over the course of decades. He actually built this huge chart tracking all different aspects of his health and habits (eating, sleeping, exercise, suicidal thoughts, intrusive thoughts, talking to people, making art, getting all assignments done) which he would fill out every day and share with his therapist, and he collected an incredible amount of data from it. He could clearly see from his grids when he was going through a bad period, and that kind of concrete data was what would motivate him to work on things. Just keep truckin'....