Selling Bitcoin would always be a stupid decision, because the price could be always higher. But there are people who just don't want to invest anymore and they are retiring, for an example, people who bought Bitcoins for $1 each don't need to wait anymore, they are already rich and they can retire.
It's only become worst decision when you keep buying high and sell it low repeatedly, other than that just a fine thing. People just have a narrow-minded when it comes to calculate how Bitcoin supply limited causing the price , the value of Bitcoin itself in the future whenever every single Bitcoin has mined could guarantee a hell high price without considering how it could worth nothing if there's no one interested anymore in Bitcoin later , I do put my faith in Bitcoin but always have a plan B to anticipate unexpected things, so I won't call it that way to those people who selling Bitcoin now or later .