You're free to have your own opinion, but as far as I'm concerned, once you're dead, that's it. When we die, we're no different from an animal lying dead by the side of the road. The only life we'll ever experience is the one we're living right now. Life after death is just a myth.
Your letter deeply saddened me, because it means you are living without hope — hope for this life, and hope for the life to come. Have you honestly faced how empty and meaningless this will make your life?
Right now, this may not bother you, because you’re young, healthy and energetic (as you say elsewhere in your letter). But what will happen if something goes wrong — if you have a serious accident, for example, or you lose your health, or someone you love abandons you? Or what will happen once old age creeps up on you, with all of its problems and disabilities? Then you’ll be facing the future without any hope — and that is a terrible thought. You’ll be like those of whom the Bible speaks, who are “without hope and without God in the world” (Ephesians 2:12).
But life doesn’t have to be this way! God loves you (even if you don’t believe it right now), and He doesn’t want you to live a hopeless life. This is why He sent His Son, Jesus Christ, into the world. By His death and resurrection, He opened heaven’s door for us. In Christ there is hope!
I can’t help but wonder, however, if your real problem is that down inside you want to run your own life, and you fear giving your life to Christ. If so, face it honestly, and by faith turn to Jesus Christ and discover the hope and peace He alone gives.