There are no rules in love and if you've tried your best, TRY to let go.
Unfortunately this is not a perfect world. bad things happen to "good" people all the time.
This world is beautiful and yet ugly. The dreams we have are sweet and yet bitter. That is what this world is.
However, we live our lives the way we want and to our hearts' command.
What matters is not what is out there waiting for you but rather what is there in your heart that is yearning for.
Very often we do not seems to distinguish between what the heart wants and what we think is out there for us.
But again, we are human and human do make mistakes.
You probably did, he did, and maybe so are we now.