When we started out, did we know what we were doing? We do now.
A bit of posturing and pretense may be needed to launch a life. Posture and pretense become performance. The untested ideal becomes the verified real. At the start of a life scant is the evidence that you can do what you dream: you must believe beyond the evidence if you are to have a shot.
And so I beg to differ with W. K. Clifford:
For a couple of rather more technical treatments, see here.