if you are merely the sum of your memories and there is no afterlife and you simply cease to be then what is the point to living your life? When you die it might as well be as though you never lived right? so why even bother with dealing with it.
As a former atheist, I'll give you my perspective. I was severly depressed when I was an atheist. When I was suicidal, I went to counseling. What I learned there was not to hurt myself because of my circumstances, and I extended this idea to taking my pains and frustrations out on other people. I was quite a vicious and cold person. I wouldn't kill anyone, only because of my view on death. I didn't believe in heaven or hell, or any sort of afterlife, and that's the only reason I didn't kill anyone. I didn't want to kill them, because to me, that would be the end. I wanted them to live and feel pain.
The only thing that really kept me going was graduating high school and going on to college. I went to a college that was quite a distance from where I was (I think only 1 other person that I knew in high school went there), but still in the same state. I viewed it as a fresh start, that it was going to be better. I spent every second in high school thinking about how much I hated everyone and everything about that school. For the most part, college was a lot better. The only person in college that believed me when I told him about my life in high school was my roommate freshmen year, and because he was coming off the end of my high school life.
There were still some things about me. I knew that whenever I wanted, I could still return to being the person I was in high school. I had friends, but none of them were really close. I also still really hated being touched, in any way outside of a handshake (something else I picked up during my atheist years). A pat on the back, hugs, or even someone putting their arm around my shoulder like friends do in photos, I couldn't stand it. In my 4th year of college I went on a mission trip. Many of my friends went in previous years and always came back talking about how great it was. I'd never been on one, so I wanted to try it myself. To make an even longer story short, one night on the mission trip, I had an evil spirit cast out of me in the name of Jesus Christ, and I literally changed overnight. I was no longer afraid to have close friends (I vowed to myself a year before not to have close friends again) and I actually enjoyed being touched and hugged by my friends.
Even if someone does find evidence to support atheism and totally disproves Christianity (it's never been done before, and given my encounters with atheists, I'm not expecting anything new or rational to emerge from them anytime soon), I would still not go back to being an atheist. It's dangerous not just for me, but for everyone around me. I'm thankful everyday that I'm not who I once was.