to try to achieve something that is very difficult.
If you want success, you have to reach for the moon.
reach for the moon
To set one's goals or ambitions very high; to try to attain or achieve something particularly difficult. My parents always taught me to reach for the moon when I was growing up—that I could be anything I set my mind to!With all that money, you could do whatever you want. Reach for the moon, kiddo!