"I fell in love once, if love be that cruelty which takes us straight to the gates of Paradise only to remind us they are closed for ever".
(Jeanette Winterson, Sexing The Cherry)
But I don't think it doesn't have to be that way. Here is something I found recently
"Many people believe that a person who has multiple loves can’t give their “whole heart” to any person. The belief goes that if you love one person, you can express your love wholeheartedly, but if you love multiple people, your love is divided up and is therefore not as deep. This is based on the “starvation model” of love—that is, you only have a limited amount of love, and if you give your love to one person, there is none left to give to anyone else—so if you fall in love with another person, you have to “pay” for it by withdrawing your love from the first person.
Love is not the same thing as money. With money, you have only a limited amount to spend, and when you give it to one person you have less left to give to another. But love behaves in wonderful and unpredictable and counterintuitive ways. When you love more than one person, you soon realize that the more love you give away, the more love you have to give. Yes, you CAN give your whole heart to more than one person, and when you do, you realize it’s the most beautiful feeling in all the world.
Don’t think of the contents of your heart the way you think of the contents of your wallet; it doesn’t work like that."
Which is pretty much what Junhong told me years ago when he was little!