1. BACK OUT! When you find yourself over your head in ideas, put some aside. I'm not saying you can only work on one story at a time, but keep to a limit and don't feel obligated to follow through on every crazy idea. If you have too many ideas- back out of some of them before your life suffers...
2. Prioritize- maybe you won't need to make a list (I always think it through in my head), but you will need some way of figuring out which works to back out of. It may not seem important, because all ideas are good, but you really should prioritize your ideas. For instance, if you have deadlines for certain works, definitely put them first. Also, you might find that your original ideas are best kept towards the top of the list. These are usually the most thought through ideas, so they will have the best results.
3. Think it through (Again)- I know you've already prioritized by this point, but it's probably best to think it through again. The items at the top of your list are usually there for practical reasons at this point, but do you really think you can follow through with these ideas? Or will you find yourself bored partway through and give up? Maybe it will be a waste of your time... or maybe not. Just think it through first. Don't start a project you won't complete if there are projects you will complete on your list.
4. Save your thoughts- The ideas you choose not to work on immediately? Yeah, best save them. Never completely trash an idea, because even if you never use it completely it may inspire greatness later on. Maybe you should start a notebook or a document in which you record a brief summary of your idea, or an outline of it.
5. Forget about it all! Don't keep thinking about these ideas which you have pushed aside (push them aside!). You need to forget about them and focus on your main projects, otherwise you'll end up right back in the same place. Forget about them... They don't exist!