"Failure is merely proof that the desire was not strong enough."
Now, I don't in general approve of this kind of sentiment. It seems to me rather too aggressively go-getting, and perhaps dangerously delusional. Much of the time, failure is simply proof that something was indeed impossible - and shouldn't have been attempted in the first place. However, I like this particular expression because it occurs in a favourite film of mine, The Hairdresser's Husband, where it is illustrated by a charming fable.