What do you do when you realize this is all there is? That my circumstances, combined with my personality, could have come to no other result than the life I am living now. All things conspired, as if on purpose, to bring me to this point. One change here or there could have steered my life otherwise; one choice or one chance could have changed my life. But the truth that I am where I am means that none of the circumstances of my life would have been any different. I say that even without the bitterness that usually accompanies it. It's just reason. If it could have happened differently, it would have.
What if Hitler had changed his mind about Barbarossa? But he didn't. He couldn't have, because his past is immutable and all circumstances led to that decision. Hitler will always have chosen Barbarossa. I will always have broken Jane's heart. Nothing in all my life, gathered at that moment, not all my wisdom, nothing would have prepared me to have acted any differently than I did. If I chose to live my life a second time, Jane's heart still would have been broken. And now, and for all this life, I will have written this blog. Nothing in my life would have changed the circumstances of now, because if they were going to, they would have.
So the rest of my life is written already, really, as is yours and everyone else's. Random events occur that direct events in their way, but they are no more immutable than the laws of motion. The laws of the universe are right now working to send an asteroid our way that will end all higher life on earth. We don't know when it will strike, but it is following a course right now that avoids all paths but our own.
So whoever you are is whoever you are. Nothing would have changed you. You will have always had the experiences and genetics that combined to make you who you are.
So if you're dismally unhappy, and you realize, this is as good as it gets...what then?