Is believing in yourself, despite evidence to the contrary a good thing?

A few years ago, I created a self image of myself as a rubber duck. My thinking behind this was. Rubber ducks rest calmly on top of the water and when the waves hit and the evils of this world rorce its head beneath the water, the rubber duck always comes out on top. You can force a rubber duck down with your hand, but the second that the pressure is released, he plops back to the top. I liked this immage, and since I am now 52 and still floating, I feel like like this self image of myself is justified. But surviving and thriving are not exactly the same...I have always been an under-achiever. And my rubber duck self immage fails to lift me above the norms of my menial existance. Should I cast out my self image of being a rubber duck and begin picturine myself as "Destructor Man"(A 40 foot robot that destroys everything that gets in the way of his goals)?