Much of our fear of our own creativity is the fear of the unknown.
If I am fully creative, what will it mean? What will happen to me and to others? We have some pretty awful notions about what could happen. So, rather than find out, we decide to stay blocked. This is seldom a conscious decision. It is more often an unconscious response to internalized negative beliefs.
Negative beliefs are exactly that: beliefs, not facts. The world was never flat, although everyone believed it was. You are not dumb, crazy, grandiose or silly just because you falsely believe yourself to be.