A Brief on Existence
All we have is our brain. Without your brain, you would be unaware of everything, but with your brain, you can imagine some amazing things. Because the brain is so sophisticated, we are able to use it for everything we do, say, or think. There is nothing beyond your brain that sends signals to your body, there isn't an outside source. It is the brain that allows you to create concepts such as the supernatural, a spirit, and a soul. These things do not exist beyond the brain because it is the brain that generated the idea in the first place. Supernatural and spiritual realms only exist in the minds of those who subscribe to them, they do not exist as separate entities that are open for discovery.
Your brain will decay, rot, and die-this is the end of awareness, you no longer exist. It is a biological organism that will not survive death, that is the unstoppable nature of biology. People have a difficult time coming to terms with that fact, they want to think there is something beyond death. While the concept of an afterlife is attractive, in certain contexts, it is still an idea generated by your brain which will cease to exist upon death. You won't know that you are dead because your brain won't be around to tell you that you're dead. Our awareness is the result of brain function, to put it simply, but that function is an astounding process that should be celebrated while we are able to enjoy it.