What happens when love tips over into the infatuated state of ‘limerence’?

‘Some of us fall into wild, ecstatic infatuations that feel like a different operational mode for the brain’: Tom Bellamy. Photograph: Fabio De Paola/The Observer

I never really gave much thought to the nature of love until it became a problem.

Throughout adolescence I suffered through a series of intense, mostly unrequited crushes, but just assumed this was the exquisite agony of desire that poets and lyricists work so hard to capture in words.