This is what stops me. I definitely have at least societally caused ADD (i.e. internet is just a click away full of ways to waste the time away), but probably a bit more than that, and I have a close family member with diagnosed ADHD, so I probably could get it diagnosed and get meds for it...but I'm a little afraid I'll lose one of the good things about it, which is my brain keeps bouncing around from idea to idea and comes up with all sorts of interesting things.
Now being able to stay focused to get those finished enough to get them out the door and released on the world is another thing entirely, and I seem to be having more difficulty with that now that I'm older and have more natural distractions such as two dogs that always want my attention at the worst times :)
But yeah, always had issues with deadlines, getting to places on time, impulse control, focusing on things I don't care enough about (i.e. work), etc. I've muddled through anyway and done alright for myself, at least so far, but I might get more accomplished with some medication.
But then what if I stop coming up with cool game designs and stories and music as a result?
The other thing that stops me is that close family member had some bad reactions to ADHD meds (both physical and mental), so that also gives me pause, since we share a lot of the same genes.