The title appears counter-intuitive -- by restricting yourself you will be freer. It's absolutely true though. Discipline is essential to a purposeful life. It frees you from distraction and provides you with focus and time. Discipline isn't about forcing yourself to do things that are undesirable. It is about building the life that you want, whatever that happens to be.
Discipline has an undeserved bad reputation, especially in an instant gratification culture. It conjures up images of self-denial and subjection to unpleasant experiences. While this isn't entirely false (not every moment of the disciplined life is ecstasy), discipline yields enormous long-term benefits.
The disciplined life isn't easy. It requires choices and you will have to forgo some things (but what are you really missing?). By making such choices and having the discipline to stick to them, you will be free from that which you didn't deem important enough to choose, i.e. the unnecessary distractions that previously limited your life. With that freedom, you can create a life that brings you purpose and meaning.
When deciding whether to choose the disciplined life, consider the following: would you rather watch someone else live out his dreams or spend that time achieving yours? Makes the choice pretty easy doesn't it?