The world calls sex love. It is the pretty much the opposite of Biblical love.
There is sex, there is love, there are the two together, and all of these conditions can cause problems.
Add, the cases where A comes to love B but B doesn’t love A (or much less so), but B gets to have sex with A.
And then there are the cases where both love and sex have a time limit.
Life gets messy. And tragic. And often very amusing.