The worst part isn't when the game launches and does poorly, but during development.

Most devs are passionate gamers themselves, and even if our own priduct doesn't turn out great, doesn't mean we don't know what makes a good game. So most of us know that the product we're working on isn't gonna be a GOTY.

There's a few stages to it, similar to the stages of grief:

    Denial: "If I pull extra hours, I can fix this feature. We can turn this around."

    Anger: Frustration and anger that's usually directed towards upper management ("why did we have to make this decision? why don't we have enough staff? why are we launching in three months?"

    Acceptance: "Whatever, you can't always bat 1000. As long as my job is secure after all this, I'm fine."

And worst of all, apathy, where the passion you once had has been sapped from you, and what you thought was a dream job, has turned into just another routine motion you go through.