I don't think this means what you think it does.

You are happy when you buy a boat because you'll be experiencing new stuff which you haven't before.

You are happy when you sell it, not because the boat was a pain in the ass to maintain. It is because you have what you wanted from the boat and you are happy with the memories you have. I haven't been there done that but I imagine it makes the person even happier because you get some extra cash too by selling it.

If a person is happy just because he is getting rid of his boat, he either bought the wrong boat in the first place or he is simply bored.

I can't imagine myself being happy for selling my favorite toy.