There are personal reasons to sell a stock. And there are investing-related reasons to sell a stock.
Most often, personal finance drives the decision to sell a stock because you need the money. You need to pay your child's tuition. You need to pay the IRS. Your dog tore her ACL and she's going to need a bionic knee (apparently). One reason we all invest is to have the money we need when we need it.
Whenever you sell, though, you're giving up the long-term growth potential of your investment capital. There are times when you want or need to do that, but it's important to keep that general principle in mind.
Source Fool.com