The price is really so volatile that it's so hard to know when to sell. Maybe when it reaches $1,000 there would be multitudes of people selling enormous amounts of bitcoins. If it does happen the supply would boost and the buy demand will drop and that would result to a correction then probably that would be the best time to buy a lot of bitcoins.
Volatility doesn't really matter in this case. All that matters is how much profit will you make if you sell now. If you sell right now and you have made like $300 profit per coin, then you have done well. If you believe that the chances are high that when the price reaches $1000 again people will start securing profits like there is no tomorrow, then you are better off securing profits right now. From current price to $1000 is just a $30 difference. I always say better safe than sorry. I have already taken profits at around $950-$960 so from now on I can happily watch the price either go up or down.