You can visit.
I rehomed a gorgeous black/turquoise betta in 2005 to one of my friends bc she really wanted him and the friend I'd originally gifted him to just didn't take care of him at all.
The initial friend was an officemate and I took care of him along with the fish on my desk. Then I went away for almost a month. I left treated water and detailed instructions.
When I came back, He was close to death.
So I rehomed him. And whenever I'd visit he would do an especially acrobatic dance for me!
"He never does that for anyone else!"
He lived until 2010. He was pretty big so probably a year old in 2004 at the time of his purchase.
Even if fish feel sadness, like human beings their emotions will pass.