As the proverb goes, it is always the right time to sell and to buy

If you were unlucky to enter the market at highs, I think you may want to sell part of your stash. I don't know how much you have so the actual percentages may vary (and would depend on your entry point), but by selling some of your coins you will make situation more manageable and acceptable overall to yourself. If the price continues to go down, you can buy back again a part of the coins you sold earlier. It is unlikely that Bitcoin is going to die any time soon, thus by taking the opportunity of playing on Bitcoin volatility you can decrease your losses and ultimately turn profitable