Because you cannot do it alone.
No one has ever succeeded by himself.
Steve Jobs had Steve Wozniak when he was starting Apple, Tim Cook for managing the day-to-day operations at the company, and Jony Ive for remarkable product design to name a few.
Michael Jordan had Scottie Pippen with him on the court and Phil Jackson on the sidelines in his six championships.
Roger Federer have Stefan Edberg and Swiss Davis Cup captain, Severin Luthi, as his coaches. Even before Stefan Edberg, he had Paul Annacone and other coaches.
The Beatles had, well, each other.
How about you? Who are the people around you helping you achieve your dreams?
You don't have to do it alone.