One of the important aspects of living with ADHD is getting overwhelmed by thoughts. This is usually a major pain in the ass. When left unchecked it usually leads to a lot of confusion very painfully visible to people around you. This made most of my school life very tormenting. Despite being an "A" student, I was always completely lost.
This got better when I found computers. A book I found while sitting in the wrong classroom turned things around for me. My thoughts got channeled, things started becoming a lot more clearer when I wasn't thinking of 10 random things at a time. I was still thinking of 10 things at a time, but it was now manageable; it was interesting. I wasn't fighting the trains of thought anymore, I was enjoying the ride.
This was alright while it was fun and games, but it became a problem again when I entered software development as a profession. Now I had to focus on things for extended duration of time; which usually was more than my interest span. It was a struggle again. I got over that period though; my current solution is to bring more accountability for my work, for which right now, I am doing a day job.
During my period of struggle, I did a lot of fight to stay focused. I fought to not let distractions come in; I blocked sites, tried several time-boxing techniques; most things worked, but for a small duration of time. The fight did me more bad than good. Exploring things is what make me happy, when I took that away from myself, the frustration that built up as a result threw me in a pit of despair.
My recommendation to anyone finding [her|him]self in my shoes is to not fight it all the time. Do whatever you feel like every once in a while. It is very important to keep feeling happy. Trust yourself that you'll manage to get important things done in time. However, you need to build/earn this trust. Read my previous post for some tips on how I do it.
When you find something you feel passionate about, the multiple trains of thought kinda all go in the same direction. They're all interesting, and you want to ride them all. If you fight to ride one (or few) of them, you're gonna give yourself a hard time. Instinct to hop on each one of them until another one is more interesting isn't all that evil. I'll be writing more posts on how I do that (i.e tools and techniques I use), I don't have time right now, and am losing interest in writing this post. Try to trust yourself that you'll come back to what you're pausing, have means that allow you to hop b/w different things, and try to be at peace with the fact that this is simply how you operate. It might look chaotic to others, you'll still not be "normal", but you'll be a whole lot happy, and hopefully satisfied.
In my current setup I have tens of different things I am time-sharing on, and am still delivering satisfactory value in my work. It is certainly possible for you to not fight tooth and nail with your way of thinking and have a satisfactory career (at least in Software Development).