Don't hold back.
Or...
Just let go.
Do it.
Do that one thing you never have the nerve to do.
Face your fears.
Grab the bull by its horns / balls.
If we don't, we'll always ask 'what if''. People's biggest regrets are the things that they didn't do.
I don't want to wait for life.
What I want, I want right now. No one ever thinks 'ooh, I really want a cup of tea... in two hours'. Or 'I really want to help the environment... when I have my own house'. If you want it, you do it.
So just do it.