The concept is simple: sell what you need of the holding in question in order to recoup your initial capital and then you can keep the remaining shares for free (assuming you still believe in the story). And you can hang on to those free shares for as long as you want.
Of course make sure you understand any potential tax implications of selling (if it's in an IRA then that's even better) but at the end of the day we invest to make money and there's nothing wrong with that. While I consider myself an investor who takes the long view, I also consider myself an investor who's always paying attention to the options that may exist. The longer you invest the greater the chances you'll run into a situation like this and the bottom line is that it's always OK to sell as long as you understand why you're doing it. House money can allow you to hold onto that position (regardless the size) for as long as you want and if it's one thing most multi-baggers require it's time. This is one way you can have your cake and eat it too.