It's not how they feel at all. Or, if they do actually feel that way... it's inadvertently the "fake it till you make it" where they have done this for so long

It's not how they feel at all. Or, if they do actually feel that way... it's inadvertently the "fake it till you make it" where they have done this for so long and so intensely that they've tricked themselves into feeling it. It's likely the origin of some large fraction of mental illnesses.