I had to open this thread. Ugh. I have a lot of conflicting ideas in regards to this question. I once had a theory I believed summed it all up quite nicely and inclusively. The purpose of life is to find your own answer.
But as time went on I started finding my own ideas, and finding my own answers.
I'm spiritually questioning or confused. I don't know if I'm an atheist, agnostic, or spiritual. I therefore have various ideas to answer this question.
From an atheistic point of view, the purpose of life is to mature, reproduce (continue your genes and ensure the survival of your species), and die. Even death has an incredibly important purpose and life itself does not end there, because your body is left behind to return matter and energy to the universe and continue the process of life.
From an agnostic point of view, the purpose of life, simply put as before, is to find your own answer. There is no single, sole purpose of life as we all have our own needs and beliefs which cannot be forced upon anyone by anyone else.
From a spiritual point of view, I believe the purpose of life is to grow, to understand, to love, and to fight. To suffer in order to achieve happiness. To love yourself, others, the world, and the universe unconditionally. To remove selfish actions and to sacrifice yourself for the greater good. To continually learn about yourself, others, the world, and the universe both in a physical and spiritual way.
So, there are my three thoughts on the purpose of life. I'm often in a conflict between them but for the most part I can view them in unison. The first and third fit with the second because these are my answers. The first fits with the third because it is but one, physical way of understanding the purpose of life. The third, I think, envelopes the first in a feel-good, hippie, universalist kind of way.