http://www.chess.com/livechess/game.html?id=302736733

WE ALL MAKE BLUNDERS AND OF COURSE YOU FEEL BADLY

Er...because they're bad?

What a great question. Let me study this thoroughly and get back to you.

Okay TM, why do you need to study this?  Is it because, by thinking about a problem comprehensively, you might better arrive at a solution?

Not your question, Tony. The OP's title. I need to start drinking heavily to improve my comprehension of it.

Where's trysts when you need her? We could brainstorm it.

Jeez TM, there went my droll attempt for naught...

Andy, losing the initative may lead you to lose.

Kaufman, now that I am fairly liqueified I have come to the conclusion, after much deep study, that certain bad moves or blunders are only considered that if the opponent hasn't previously arrived at the solution that those particular moves are blunders. 

Additionally, losing the initiative can apparently be rather a bad thing as well.