because the price is down and I want to sell it when price of bitcoin will rise to 650$-700$
Holding your bitcoin is safer investment because you just hold your bitcoin and wait until your goal prices and sell it.
It will probably take quite a while for the price to get that high again
Last 2 weeks ago it jumped to $620 up. A $15-20 is still profit. You can buy back fast once it goes down. If you got 5btc then it is almost a $100 profit. For big investors a little movement are crucial.
The profit is really noticeable for those big fish since even a $10 increase, the profit is good to considered.
For small players, they need at least around $100 price rally increase so that it's worth to sold. Well that is for my own preference as others have different price to considered they are on profit.