(Originally posted Aug. 25, 2006, on Perspectives)
Some people ask the question, "What is life for?" As an atheist and according to the way I think of the universe, there is no ultimate answer to that question. Imagining life has a purpose is just a coping mechanism we utilize to prevent depression and to keep motivated.
Natural selection chose our ancestors because they had a desire to live and that gave them an advantage in producing offspring. Most of the time, we have a strong desire to live (possible exceptions are when we are depressed, in pain, or terminally ill). I believe our default programming will search for a meaning to life to justify the effort and discomfort we sometimes feel. Due to our large forebrains we, at minimum, have the impression that we can choose to override our default programming and accept one of the meanings preached around us, choose a different meaning for our lives, or choose to give life no meaning at all. We certainly don't have to give life meaning if we can tolerate the implications.
For me, I have "chosen" to give my life meaning. I believe that there is no eternal consciousness that will remember or appreciate anything that took place on this planet once we are all dead and gone. And "heaven" knows my life has no meaning to any of the organisms on this planet that cannot comprehend "meaning". That is not to say that my life does not affect or influence the lives of at least some non-conscious organisms, but they don't understand enough to care whether I live or die. So, meaning seems to only exist for humans, and perhaps only a subset of them (existentialists and the very religious - I don't know).
In any case, I choose for my life to matter to me and I know that my life matters to my loved ones, and I choose to care about their feelings. What matters to them, matters to me. To help illustrate this, imagine your 4-year-old coming to your side quite upset because she is scared of the dark. Now you know that there is no need to get upset about the dark. You could easily dismiss her fears as being irrational and send her on her way. But, instead because you love her, what matters to her matters to you. You choose to comfort her and reassure her and allow yourself to feel for her. Remember the movie "What Dreams May Come"? The main character could not save his wife from her depression until he allowed himself to empathize and join her in her suffering, then they both could leave the suffering.
I am rambling, but I give my life meaning through my relationships and by helping people learn to be happy.