I did not intend to say "follow your bliss" but the simple fact is, if you're confronted with multiple ideas, it is the rare individual who can develop each fully and simultaneously. Yes, write down the ideas you have -- I have a notebook for each of mine that I think might be a novel, a trick taught to me by a member of my writing group, and a closet door covered with post-its and odd pieces of papers for other ideas -- but when it comes time to write, you have to choose which one(s) to focus on and develop. Sometimes the process of developing an idea leads to deadends, sometimes it goes in a direction you did not intend it to go, sometimes everything goes smoothly. The thing is, people, because they are people, tend to beat themselve up over time wasted if things don't go exactly according to plan or if they don't have a product to show for their effort. What we have to realize is that even when this happens, if we learn from our efforts, then we have still made some gain.