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.
There's a book called "Tiny Habits" which goes into this more.
I've also tried to use this when building my own habits and it's been fairly successful. When most people want to start something they get all excited about it and jump in with both feet. And then they burnout and stop. It's the New Years Resolution gym effect. After New Years, gyms are full of people who set a goal to exercise 5 days per week. After 3 weeks the gym is back to normal as all those people burnt out and realized they couldn't keep it up.
The brain needs time to adjust to change. I'll start out with something really simple like exercising one day per week for 15 minutes. Then after a few weeks when it starts to feel routine, I'll add another day and wait a few weeks. Eventually I find that I reach this equilibrium point where the time I'm putting in is enough and it's easy to maintain that habit.
