I regretted selling the first rifle I let go and for a while I was totally against selling any guns but after a while I realized I had a gun or two that I never shot and/or just plain didn't like. I started selling my crap guns to buy better versions now I just sell anything I want to sell. I don't do it on a whim though, if I sell a gun it's gun I don't shoot and don't have much use for and don't have any attachment to. It's also a gun I can replace easily if I later regret selling it.
I don't collect guns, I accumulate them.