If self-handicapping to preserve your self-image with respect to one thing impairs your performance in many situations, then one approach would be to do some very rigorous testing, e.g. if one is concerned about psychometric intelligence, one could take several psychologist-administered WAIS-IV IQ tests on different days.

"Belief in belief in religious faith and self-confidence seem to be two areas in which we can be simultaneously right and wrong: expressing a biased position on a superficial level while holding an accurate position on a deeper level."

This is also relevant for Caplan's model of rational irrationality in political beliefs.