What was the final "trigger" that convinced you to become an atheist?
For me it was the realization that the Bible is NOT the "Word of God." I had always disbelieved all other Gods, so when I realized that the God of the Bible isn't real I was left with a default of zero gods. I actually usually refer to myself as an agnostic, though, since there may be a slight possibility of a deist sort of God, but I don't normally lean toward that view and I have no specific God belief, so I guess I'm technically an atheist.
How did your decision to become an atheist affect your life?
I wouldn't call it a "decision." I didn't decide or choose to stop believing, I simply couldn't believe anymore due to what I was learning about the Bible. For the most part I haven't come out family and friends as a nonbeliever, but it has made some things a little awkward
Atheism seems to result from an increase in knowledge. I have never heard of a person who genuinely lost faith due to an emotional response to trauma.
Mine was also an increase in knowledge, but I would suspect that there are people who lose faith due to an emotional response to trauma. Those whose faith would be lost emotionally, though, could have their faith restored emotionally as well, and I suspect that most who go back to religion would fall into this category. Those of us whose loss of faith is due to what we've learned would be less inclined to return, because we can't toss what we've learned out the window.