I agree with you, panic always lead to wrong decision. Keep calm. After that, Look back your coin, if it's a good coin, you should hold or even buy more coins with low price and wait for recovery. You will get a big profit. But if your coin is not good or it has a bad new problem. You should sell immediately.

If you panic the best thing to do is to get up and get some fresh air do not take any impulsive decisions, you are only going to make a mistake, so you are going to make a bad situation even worst by making and additional mistake, besides most people panic when they see the price of bitcoin going down without understanding that most of the time the price goes back to normal after a few days.
Yeah get some rest and get back later when you feel you are cool enough ,
That's true about don't make things worse when the situation has been ruined , people always forced themseleves ,
Push the limit principle isn't fit in this kind situation ,
You need to have an extra patient , that's actually the key of trading success .
It may be difficult to maintain our cool when the price is going down but we must remember why we got into bitcoin in the first place, bitcoin is very volatile but we are here because bitcoin in the long run only does one thing and that is to go up, we must remember that, once you remember that the only correct thing to do when you make a bad trade in bitcoin is to hold and maintain your position.