The bond that developed between you and Leo is exceedingly intense. He was your "first love" and, in a sense, he was "forbidden fruit." The possibilities of "what might have been" are very tantalizing to ponder and can be absolutely haunting.
For some problems in our lives there simply is no satisfactory solution.
What you're experiencing is very common; in men as well. Foolishness in choices often produces consequences which persist for many, many years. It is only in old age that we eventually find relief. When wisdom finally takes hold.
Our next lives will be much different.