Depends if you need the money. I'm assuming you don't need the money since you took on a risky investment like bit coins. If this is the case, just hold it. Two things will happen. It will either go to zero, at which point, hey, you didn't need the money anyway. Or it will become the standard currency of some nations in 20 years, at which point your face will be on one of the "coins." (Albeit as a string of zeros and ones :). Last point: people said the same thing about the price of gold, when it broke $100.
Well, it really depends on how much you have. Let's say you have a 100 bitcoins. Selling half now could give you a good payout, while still maintaining your investment.
But let's look at some statistics. The most bitcoin was worth, at its peak, was around a 1,000 dollars. But the value dropped a lot, and partly because people lost confidence in it surrounding the events of Silk Road. It's around 600 now, but a few months ago or so it was down to around 300. So the price of bitcoin goes up and it goes down, and it's influenced by a lot of factors. A lot of people probably sold their bitcoins once it dropped down to around that 300 mark, but now it doubled in value again so yeah.
Secondly, bitcoin is becoming more popular, not less. They now have ATM machines for bitcoin specifically. They opened one in Norway, one in Toronto, Canada, and another in Canada that's a couple hours away from where I live. So it's still growing, still becoming more popular, and more and more people are leaning of it daily.
Bitcoin has also been responsible for many alternative coins, such as Litecoin as you probably know of. And darkcoin, which is gaining a lot of traction. I've heard of more and more people actually buying real items with it, and heard of a bar in the U.K that accepts bitcoins.
So as far as I see it, it'd be a very unwise decision to rid of your bitcoins and throw in the towel. It's risky, like any investment, because you just don't know the future of it. And it'd really suck if you woke up one day and it was worth nothing. But it's like rooting for that boxer in his prime. He's still going strong, winning some titles, even though he had some tough luck here and there. But he's in the game and going strong. Just monitor the progress of it, the value of it, and if you're worried sell some of your bitcoins but hold on to enough so that you won't regret it if the value skyrockets in the next couple years.
It depends why you bought it. If you are making a small profit in a short period of time then take it (you don't get poor by taking a profit, sell and regret, but sell etc.)
However if you believe in the fifth protocol theory then just sit on it and forget about it for a couple of years.
Makes sense :)
Everyone is saying that Bitcoin has saturated at $600, so if it isn't going up, I might as well sell it and get it over with, right?