I know it's the mantra, but as somebody in a similar situation, I can tell you there are 2 pieces of advice leading up to my imminent launch.
1) Find a partner - I've had a LOT of false starts on projects that were sure to be the next big thing. I would get an idea, work hard on it, overthink everything, convince myself it was destined to be a failure, and then start on something else. I watched idly as I saw my ideas implemented by other companies, some with very large exits, some making large profits, and some flops. I invariably regretted whatever reason I had justified to myself for losing steam on it before.
I found a likeminded individual who is motivated, and is good in all the areas I'm not (and better in some of the areas I am). From first-hand experience, it's a lot harder to lose focus or succumb to wanderlust when you have somebody next to you making progress. His progress motivates me. My progress motivates him. We both have skin in the game, and we're both moving forward at a pace I never have before.
The other piece of advice? Cancel cable. My TV broke, and I found myself being extremely productive while I was waiting for a repairman to come out. So productive, in fact, that I called and cancelled on him.
I still get most of what I watch from Hulu or other sites, but now the TV is background noise while I'm programming, and far less of a distraction than something that I needed to leave the room for.