Kickballhead - think about that tree for a moment, and all the sheets of paper it's become since the tree died all those years ago. At some point that paper will rot away to dust. That dust may become part of another tree, an insect, even a drop of water that causes a reaction in another atom of dust to create another living thing, or a rock for something to grow from, or part of something that another person eats and is nourished by before becoming part of a sperm cell ... and so life goes.
My scientific details may somewhat askew, but the principle is fact. Every atom in the cosmos lives on, becomes something (or even someone) else - just not consciously, as far as I know.
And that's it really - we don't know what happens to our 'spirit' after death. Some get by on the belief that they will go to heaven or hell, some believe in purely physical and some, like me, remain open on the question. The truth remains, though, that we should be living life for life's sake and not with a constant view to what's at the end of it.