Go forward or Hold back?

I have a question for u.
If u have a dream or passion that is ridiculously impossible, do u go ahead with it or u hold back and maybe, just maybe wait for the right moment that God knows when will come?

I bet most of u will say: Go for it!

But, is it that easy? like I said, the situation is, this dream/passion is hands down impossible. So, what say u?
Maybe I should put up a situation so that u can visualized n make decision, unfortunately, I can't think of any good one right now, sorry :)

I think I should hold back, idk....