Bleuuuurrrrrggggghhhh

What the term for when you have a great creative idea but it doesn't quite come out the way you envisioned?  I keep having ideas at the moment which I'm kinda keeping under my hat as I'm not sure if they are gonna work and I'm inching closer to something worthwhile but its hard work.  I have all these ideas but when I try them they aren't quite as good as they should be or I want them to be.  I'm wondering if I'm moving towards something worthwhile or wasting my time.  I guess I'll have to plough on and give it a shot and see it through.  What do you think?  I know its hard to help as I'm being delibrately vague but is it better to aim for something and miss or to admit when you are beaten?  Guess I have to think, what would I want my kids to do in this situation, quit or try it?