Reality is of course a man made concept. (at least as far as we know). The key thing about believing in your reality or believing in God is the word "believe". All this word means is that its something that you hope, or think might be true but you have no actual proof of it. One can believe something without actually knowing the truth. But, who is the holder of truth? Some say its God. Can we ever know the truth about anything or is there no truth just perception?