What do you do when the nearest & dearest person to you on the earth, the love of your life, leaves you? How do you deal with that?
What do you do when you find out that your spouse is in love with someone else? Do you call it quits? Leave? Do you try to get them to fall back in love with you?
There is a word for the feeling of being "madly in love", and we'll use that word because it's easier than saying feeling madly in love with somebody else.