When we are born, we're a blank slate. We believe we can do anything (within reason). And we have no reason not to. No one, including oneself, has said otherwise.
As we get older, we pick up lies along the way. Sometimes they come from our parents, our experiences, or the society that surrounds us. They often start outside ourselves, but slowly we adopt them as our own.
"I'm not smart enough"
"I don't have good genetics for that"
"I'm not creative"
"I can't draw"
Now I'm not here to tell you can do anything. You can't. But you already know that. We accept these lies because we have come to believe them. They are mixed in with hard truths that we have to live with.
You're more powerful than you think you are. Act Accordingly" -Seth Godin
We all have lies we tell ourselves. But these lies don't serve us, they obscure the truth. It's never too late to test assumptions. You might surprise yourself.