just check some trade group and see people say about that then if they say hold we sell. they say sell we hold

I believe that you should act upon the advice of the experts. There are very less chances that their predictions result in loss. I must suggest you to remain cool and calm at the time when prices are falling down. Holding the Bitcoin at that time is most preferable thing to do instead of just getting panic and selling them at lower rates.
What you say is true. Panic sell will only bring a trader to a loss. I experienced it several times. Better to back up losses than to panic sell.
ya. if you only lose when you sell. we can use some strategy to protect our fund
I dont think so you can lose only when you sell. Basically time maters a lot at which you are selling off your coins. If they are in pumping stage and you are selling them, surely you are going to earn handsome profit but if they are going through bad time and you under emotional stress obviously you are going to lose.