I always had problems sticking to anything, I'd get enthusiastic for a month or two and then I'd get bored. Never could tidy my room etc. Not saying I've anything as severe as adhd but I had trouble with self discipline. At the start of the year I decided to try to develop a good habit, any habit, to persuade myself I could do it. I decided to exercise. I spent the first 6 weeks just with the principal of do 1 situp, or whatever. Something I could do without any effort, at home, to remove any excuse not to do it. I made a tick on the calendar the days I did it so I could see my progress, I praised myself for completion, and I made it the only priority. Don't worry about tidying or eating healthy or whatever, just do that situp every day. After about 6 weeks I was getting out of bed and immediately doing the situp without thinking, I started a proper routine like 10 minutes, still easy. It'll be 3 months next week, so I'm hoping it's actually stuck. When I get to 6 months I want to start adding something like filling the dishwasher before bed. I'm 37 and this is the first time in my life I can say I've been able to do something I'm not obligated to do and don't want to do for a long period.