Everything in life is risky. While there were predictions that BTC was going to rise astronomically in 2017 and then drop by early 2018, nobody really anticipated it could dip to about $5,000. However, there are two major risks associated with buying/selling and holding. For instance, those who sold out of panic when BTC was nothing are forever regretting doing so. On the other hand, if you decide to keep it for as long as you wish and something funny happens, you really have nothing to lose considering the amount you invested but you will also not easily forgive yourself for not selling when you had the chance of selling at the best price.
The bottom line is to listen to your heart; don't let too much greed drive your decisions. If at any time you feel you can sell because you are okay with the price, go ahead and do so. Do it with a clear conscience and be satisfied with your personal decision.