With no definition, I define your thought. I'll bring joy wherever I'm sought. There's no boundaries set for me, and I'm not a thing, though that's what you see. Inspired by form and created in time- I'm here for you to make me shine. Just a feeling that lives inside- I seek that spot where you sometimes hide. My beauty falls upon the eyes of the beholder- whether you're green or growing older. In the words of a man I know to be smart, "Whatever you do, make good ________."
What am I? Fill in the missing word:
I gave you a clue!