I was in your shoes about a year ago. I had a GMT master BLNR that was my first serious purchase years ago, and found that as I’d collected other pieces over the years I simply wasn’t wearing it.
I tried giving it a break and coming back to it weeks later several times. Every time it was the same story; I loved it, wore it for a day or two, and then back in the box and didn’t touch it for months.
Eventually I sold it and used the funds to upgrade into a Day-Date; something that actually is totally different from the rest of my collection and gets a lot of wrist time.
The way I see it the BLNR (and in your case the FOIS) are not super rare prices; we’re always going to be able to buy back another one in the future if we really regret it. Sure, you may pay more to buy it in the future, but you’ll Laos make a decent chunk of change selling it now, and if you never rebuy it you’ve only made a profit.
Hope all of this helps, just just think what you could have instead if you let this one go; does that excite you, or are you just skeptical