It's a story as old as time, can't blame a fella for chasing after a girl.
There are plenty of genuine reasons to leave a club, some people would argue money was a genuine reason, others mental wellbeing or perhaps family.
About the only thing you can guarantee is that if someone wants out,, and you make them stay, they're not going to be putting in 100% and are probably going to be bringing some team mates down with them. So that's a hard call for the club to make if it's just out to look after itself in spite of the player concerned.