In my opinion, emotional attachment can be a good thing as well as a bad thing, it all depends on the context. On the one hand, you have to be passionate about what you do for a living but on the other hand, when it’s time to exit (aka sell your domains or websites), letting emotional attachment cloud your judgement would be a mistake.
Maybe you build websites for a living.
Maybe you’re a full time domainer and build portfolios for a living.
Maybe a combination between the two.
Either way, nothing lasts forever and at one point or another, you will receive an offer that’s too good to refuse. If it’s too good to refuse… don’t refuse it.
Business is business and no matter how hard you worked in order to own great domains/websites/whatever, reason has to prevail. Use that capital to fund other projects because that’s what real entrepreneurs as well as investors have in common: they identify the best opportunities, the opportunities which can help them generate the best possible ROI.
If you’re confident that you’d be able to generate a better return by selling an asset and investing the funds in something else, do it. The bottom line is this: don’t let emotional attachment keep you from making the right business decision.
On the other hand though, don’t assume you always have to sell.
Rick Schwartz is a good example.
He only sells a few domains but when he does sell, his return definitely compensates for the lack of volume.
He doesn’t sell fewer domains than most investors because he’s emotionally attached, he sells fewer domains because that’s the strategy he considers the best choice in order to maximize results.
Some people move a high percentage of their inventory each year, some don’t.
Both approaches can and do work but I assure you that both types of successful investors have something in common: they make decisions based on the strategy they consider optimal and not because they’re influenced by emotional attachment.