Why do my stories always, or mostly, have happy ends?
The truth is that is life the way we know it. Whatever happens, good or bad, we survive and we are happy, somehow. Listen to people in the pub, one will tell a tale of awful things, but is he unhappy? No, he laughs, somehow he is still happy, he survived.
But you say sometimes everything is so awful, take a tragedy like Hamlet, at the end everybody is dead.
No, this is not true, there are still some people standing on the stage when the curtain goes down. They have survived, they are still alive and soon will be happy again.
Look back in your life at the bad times, there have been bad times. Did you have to fight? And I don't mean necessarily physically. Are you a better or stronger person for that? Did you survive? Stupid question; of course you did. Were you unhappy? Are you happy now?