Maybe God exists and maybe He doesn't, but I don't see what difference it makes. We have to figure out on our own how we want to live, and whether or not we believe in God won't change that, as far as I can tell.
If God didn’t exist, or if God existed but He didn’t care about us and was unconcerned about what happened to us—then you’d be right. Then we’d be completely on our own, and it would be left up to us to decide how we were going to live.
But God isn’t like this! Not only does He exist, but He created us, and He deeply cares what happens to us. Not only that, but He knows what is best for us—and He wants to steer us away from everything harmful and lead us into everything good. As one of the best-known Psalms says, “The Lord is my shepherd, I lack nothing. … He guides me along the right paths for his name’s sake” (Psalm 23:1,3).
How do I know God cares for us? I know it first of all through personal experience; God has demonstrated His love to me repeatedly over the course of my life. But I know it most of all because of Jesus Christ. He came down from Heaven for one reason: to demonstrate God’s love for us. He did this by giving His life so we could be reconciled to God—and this happens as we open our lives to His forgiveness and transforming power.
Don’t go through life without Christ. Instead, by faith commit your life to Him. Then discover the joy of walking with God every day—now and forever. Because He loves us we have “a living hope through the resurrection of Jesus Christ from the dead” (1 Peter 1:3).