For men have ever a likerous appetite
On lower thing to perform their delight
than on their wives, be they never so fair,
Nor never so true, nor so debonair,
Flesh is so newfangel, with mischance,
That we can in no thing have plesaunce
That tendeth unto virtue any while. Chaucer

Love creates a generous state of mind. Because love allows us to experience as pleasurable situations or physical features that we otherwise might not, it also allows us to unlearn negative associations, another plastic phenomenon.
The science of unlearning is a very new one. Because plasticity is competitive, when a person develops a neural network, it becomes efficient and self-sustaining and, like a habit, hard to unlearn.
Falling in love for the first time also means entering a new developmental stage and demands a massive amount of unlearning. When people commit to each other, they must radically alter their existing and often selfish intentions and modify all other attachments, in order to integrate the new person in their lives. Life now involves ongoing cooperation that requires a plastic reorganization of the brain centers that deal with emotions, sexuality, and the self. Millions of neural networks have to be obliterated and replaced with new ones - one reason that falling in love feels, for so many people, like a loss of identity. Falling in love may also mean falling out of love with a past love; this too requires unlearning at a neural level. Norman Doidge, M.D.

Now what could artless Jeanie do?
She had nae will to say him na:
At length she blushed a sweet consent,
And love was eye between them twa. Robert Burns

A man's heart is broken by his first love when his engagement breaks off. He looks at many women, but each pales in comparison to the fiancee he came to believe was his one true love and whose image haunts him. He cannot unlearn the pattern of attraction to that first love.

Or a woman married for twenty years becomes a young window and refuses to date. she cannot imagine she will ever fall in love again, and the idea of "replacing" her husband offends her. Years pass, and her friends tell her it is time to move on, to no avail. Norman Doidge, M.D. The Brain That changes Itself

But I do love thee! and when I love thee not, chaos is come again. Shakespeare

Love, all the hours are long
that once so fleetly flew;
I am bereft of song
Being bereft of you.
but when you come again
How nimbly time will run
To such a jocund strain,
For you and song are one. Clinton Scollard