One of the most striking things about life is that we must make choices. Everything in life is limited. Time, resources, opportunity, and so on. You can’t be everything you have ever desired to be. You can’t do everything you’ve ever wanted to do. You need to pick and choose.
Focus has a lot to do with proper prioritization. To start with, if you’re all over the place, trying to get a million things done, your attempts to focus will naturally fail. You’re doing it wrong!
Many people with overachieving potential (a lot of different talents, hobbies and interests) end up underachievers because they can’t remain focused. They chase too many rabbits at the same time. Having too many goals or one big dream that monopolizes our expectations about life can ruin our ability to act towards any goal. The result is slow to no progress.