Gandhi said, "Men often become what they believe themselves to be. If I believe I cannot do something, it makes me incapable of doing it. But when I believe I can, then I acquire the ability."
As a manager of people and processes, I talk to people for a living and it never ceases to amaze me how often we all limit ourselves by how we think. The world can often be tough on us, but too often we are harder on ourselves.
We tell ourselves that we can't do something or how hard things are for us to change, but we don't try to actually do what we what.
People do amazing things everyday, all over the world, because they know they can.
You just have to try.
Go make a sales call, put that idea on kickstarter, write that book.
People do it every day.