This happened to me last year after 16 years together/11 years married.
Initially I felt alive, it was exhilarating.
Then like youre experiencing it became overwhelming in a negative way. It started in October through a project I was linked in with and by January I was actually sick of the torment of dawn to dusk thinking of the person.
After 1 meeting where rather than the topic, I was having sexually intrusive thoughts tge whole meeting and I thought this is enough.
So I actually booked a therapist and did about 4 sessions. On the 2nd session she gave me homework to write a letter to the person, just for me to read out in therapy.
I had so much to say it was 9 pages long, it took me ages to write in amongst work and family life. I kept re-reading it to myself, to edit it and i also read it out loud to myself numerous times when i got the chance.
I was told to write everything down, lay it all out including my sexual desire, everything. Basically the full story. And to include my best case scenario with them.
As I wrote, edited, read the letter -the power was taken put of my limerance, by the end of it, once I'd completed it I felt almost indifference.
And my best case scenario at the end was sensible, along the lines "this experience has been difficult for me, but i have felt alive because of you for the first time in many years. I think you are a great person and I hope you have a great life"
Anyway i spent my 3rd session reading out my letter for 30 minutes non-stop. Then we discussed how I felt and i explained about the fascination being gone etc. I could remove myself from project however I wanted to check how I would be, I wanted my own closure.
Then i had to see them at meeting and i was able to concentrate and thankfully felt nothing.
So at 4th session with therapist I wrapped things up and I made that my last session snd made arrangements to move on from the project too. I wanted a clean break.
I do still think of them occassionaly, but more so how alive I felt, when comparing it to my rocky and passionless marriage.
I did experience that alive feeling with my husband when we were first together, ive had a great love, when some people never experience that in their lifetime. But like you theres been many external challenges that have ground down our romantic love.
I have my sensible head on that in this economy and just being a good team in general, its best to sit tight in my marriage.
Luckily for me the other person wasnt interested in me, otherwise I might not be together with my family with finacial stabilty and being part of a team with my husband etc. because if they had shown romantic interest toward me I think the limerance would have caused me to make some destructive choices.
Hope this is of intetest and of help somewhat. Good luck.