Don't throw an idea away. Of course, you can get rid of things that you absolutely know you won't use later, but any idea that seems reasonable, don't throw away. Even if that idea or small writing can't be used now, who knows, it could be the perfect thing later. Save all your writings, and if you don't keep them on paper make sure to at least keep them safely hidden in the "random writings" folder that you have on your computer, please tell me you do have a "random writings" folder on your computer!
Disclaimer: Good Ideas were never really harmed in the picture above.