Decisions like this are very dicey considering your how much the price was when you bought and the present price but for me when it goes below the $3000 mark i will have to sell.
You should always find out at what rate you had bought coins and if you are in profit then you should be happy. If you start entering losses and till what limit you can sustain it you should calculate it and then accordingly if you cannot sustain more loss you should sell it if markets looks gloomy to you.