Very good question, and one that is WAY above my pay grade. I'm just a sufferer who happens to have done enough introspection to recognize a few of our behavioural patterns, and, quite frankly, if the can of worms that is ADHD were easy to deal with, it wouldn't be a psychiatric diagnosis.

That said, I think the first step to managing any dysfunctional behaviour lies in understanding the motivational issues underpinning them. For the ADHD mind's difficulty following through and completing projects, I've personally come to suspect two major motivational hurdles are: 1) perfectionism and 2) curiosity.

Perfectionism tends to be a huge problem for follow-through since it leads to a tendency to just keep digging deeper into every little detail that could be improved upon, rather than actually setting a project schedule aimed toward producing an acceptable result and then committing to it. This tendency is a whole can of worms in itself and there are no simple ways to simply overcome perfectionism. I think it does involve a fair amount of emotional work, because perfectionism usually stems from some kind of unidentified internal insecurity. In the case of ADHD there's always a neurological aspect compounding the purely psychological problems. ADHD brains actually do work differently, after all, and sometimes it takes actual medication to alter an underlying neurological mechanism that leads to a problematic behaviour. Why Perfectionism Isn't Perfect -- and How to Overcome It

Curiosity is a weird one for sure. I'm very curious and in my experience so are most people with ADHD. How can that be a bad thing, though? Well, in the end it might boil down to competing reward signals in our brains. Which feels more rewarding to you: taking one small concrete step towards finishing a project you've almost completed, or exploring a new idea you just had, which seems to have a lot of potential? The answer to this question may have more to do with personality than any diagnosis, but it might have a lot to do with ADHD as well. In my experience, taking concrete steps toward finishing projects only feels satisfying to the ADHD brain to the extent that there is still new things to explore, discover and understand before we finish the project. In other words, we are motivated by curiosity WAY more than actual achievement. This gets us all jazzed up when it comes starting new projects, but makes it almost impossible to finish them. The closer we get to the finish line the less remains that could possibly be learned or discovered, after all, which is the only way we could satisfy our curiosity. What to do about this, then? I have even less advice here since it's something I've struggled with my entire life and still haven't found a great solution. I still think the first step to finding a solution is gaining a correct understanding of the problem, however.

I think trying to overcome our own natures alone can - almost by definition - be a losing struggle, so an important part of making progress is having the courage to admit to yourself that you sometimes need help and actually ask for it. Body doubles, accountability buddies, coaches and therapists can all help and are sometimes downright necessary. In the end I'm not a specialist or medical practitioner of any stripe, though, and those are the ones you really should be asking.

TL/DR: I just found a relatable meme, bro.