If somebody offers you an amazing opportunity but you are not sure you can do it, say yes — then learn how to do it later!
Side notes:
Sir Richard Charles Nicholas Branson is an English business magnate, investor, and author. In the 1970s he founded the Virgin Group, which today controls more than 400 companies in various fields.
Also, Richard Branson likes space exploration and is one of the few private citizens that has been there!