Unpicking your personal maladaptations helps a lot. This is how therapy and medication are so useful, particularly in tandem.

Two of my big maladaptations were using stress to drive me through, and berating myself when I didn't do as well as I knew I could. It turns out that this is quite corrosive to your wellbeing, and that wellbeing is the foundation supporting your self driven. I was consuming myself for fuel.

I've gotten a lot better at redirecting my irritation. I don't get mad at myself for not doing the washing up. I get mad at the washing up for existing. It's a subtle, but powerful difference. I still do both, far too much, but I'm getting better at it.

Lastly, remember to bask in your glories. We tend to forget to enjoy the results of our effort. We just move on, and so don't get the dopamine hit. Set aside at least 10% of the time taken to bask and feel proud of yourself. To show off and enjoy. Suddenly your brain has a positive reason to power through, rather than just avoiding a negative.

Medication definitely helps as other has said. But for me when I need something extra to get through break it up and take a break in the middle

And this is what works for me, your mileage may vary

For example if I’m writing a paper first I’ll first make an outline, intro, methods, conclusion, etc. Then I just have to fill in my bullet points with general ideas. When I’m done with that I start writing intro then take a break

Another thing is what take others 3 hours to do will take me the whole day so whenever I’m at my halfway point or I’m spinning my wheels I’m the mud (which is when I’m getting no work done with lots of thoughts or zoning out) I take my break but I tell myself “I’m doing good I deserve a break, I’m doing good I can’t burnout, I looked at my calendar I’m on track. I always give myself those reassuring pep talks because I know I can’t work fast it’s just who I am

Then I take a half hour break either playing games or walking the dogs or grabbing a snack. Something I’ve noticed is different activities will help differently. For example if I’m zoning out lll walk the dogs to get back into it. If I’m still “thinking” about the paper but finding it hard to bring myself to type it out I’ll play a game

Hope this helps, it’s really about finding what works for you and which strategies work when

Medication

Therapy (both individual and group talk therapy) helps with the emotional regulation and any childhood trauma and bad coping mechanisms you acquired by being a kid with ADD/ADHD. Medication helps with the focusing of course, both allowing you to focus for longer and sometimes (in the case of XR meds) softening the "crash" so you can have the mindfulness and focus to bring your emotional regulation tools into play and start to self regulate. I firmly believe both are necessary for some (if not most) people to be truly successful living with ADD/ADHD.

Also acceptance and self-forgiveness. Taking a nap. Or physical exercise, preferably outdoors.