I actually left the Borg because I became an atheist, not the reverse. Knowing more about the 6 major catastophic events in the history of life on Earth, then asking myself questions about the Flood...
As for the purpose of life... if you talk about the purpose of one's life, I'd say your life has the purpose you put into it, nothing more, but nothing less either. That can be as beautiful a purpose as you can imagine, and a far better one than the one any skydaddy could devise for you. Good for me since I have a big imagination ;)
If it's about the purpose of life in general, it's about the same. We think, we can assign a purpose to life with what we (all living beings) will collectively want to do of that life. There doesn't have to be an intrisinc purpose external to life itself. A purpose is not better because it has been assigned to you by somebody else, and it's not worse because it's you that has to find it by yourself. Having that purpose assigned by God only gives you the comfort of certainty, but the purpose from God won't be better, only worse. I don't want to trade beauty and value for comfort.
On a fundamental level, all species want to survive and reproduce. Then you can add other purposes, but in itself it's good enough - because it's not the destination that counts, it's the travel itself. Surviving and reproducing make that travel possible for billions of living beings that have been, are or will be incredibly blessed with the chance to experience life and assign their own purpose on top of it.
I think of it as parents think of their children - you want to give them the best chances in life, not for your own happiness, but for theirs. So we all try to advance and make the world a better place, because that allow others yet unborn to also experience that life in the best conditions possible.
It's the opposite of what most religious people believe - a Being creates others, only to ask them to live their life the way He wants, for His glory. No sane and loving parent would do that.