For each project keep an extra file where you can put all those ideas that don't quite fit. You can use them later on, or save them for other projects. Ideas are like putty, they can be molded to fit. If you are writing, for instance, and you sense that a scene is too long and maybe a whole chapter just seems to be sitting there with no reason, take it out and put it in the extras folder. Does the book read better now? Are the characters still alive? Good. You didn't need that scene. You may like it, but you didn't need it. You can always add it back in (but try not to).