Sometimes, attention problems can be corrected by taking better care of yourself. Personally, I've found my attention problems come more from ultimately not caring than from some weakness of character. It's easy to think up ideas that could be successful, but are they really for you?
For example, I've come to discover that I get motivated when solving really tough niche problems that no one else has dealt with effectively. But I couldn't care less about serving general lusers, like writing Facebook apps. I could maybe think of a cool idea for a Facebook app, and it might even be a killer one, but ultimately, I don't feel anything about serving Facebook users, harvesting their data and habits, etc.
Is it possible you're tackling the wrong projects?