imo you should never sell when you are on - with your investment. i would hold the bitcoins I have at least until I have a profit, and after that I would sell only then profit and keep the rest of the bitcoins for long term..but this really depends on you 
Bitcoin has proven to be the Baddas of all investment and this is why people love to buy even at loss. You know one strange thing when people keep selling bitcoin, it's another person that's buying every Dip and they always sell when price go up and keep doing the same thing until they collect all their dollars and get bitcoin very cheaply when they panic or react to market negatively.
I hold bitcoin, I will hold and wouldn't sell any for anyone, that way we all increasing demand and reducing supply.