I had somewhat the same situation when my employer granted me some stock options, and the stock was going up. Do I sell now and take the money, but miss future gains? Do I wait and get the future gains, if any, but also face the risk of future losses?
I decided to try to minimize my future regret. So I sold some, and kept more, and as it kept going up I sold more.
There's only one thing I regret: It reached a price that I thought was really sweet at the start of December (I don't remember which year). It was a really tempting price, but I didn't sell because I would pay too much of the gains in taxes. I wanted to wait until next year, when more of the profit would be in a lower tax bracket. Two days after I decided that, the price dropped dramatically.