I often experience panic at the time I am trading it is because the price of my trading coins change very drastically and sometimes I often can not control my mind.

No you shouldnt be doing this. Make your mind ready for the losses and profits as well. Risk is always there so your mind mustnt be shocked when loss comes to you. Keep on holding and see the prices raising and falling. Then determine whether time is good for selling or not and act accordingly. Dont be panic and only then you can have your selling, a good selling. Good luck.
According to my experience, the price of cryptocurrency can not dump more than 30-40%/day, unless the price of that coin has pumped crazy before it dumped, it is normal. But for the price of Bitcoin and top coin, this is the rule to correction of the price on the cryptocurrency market. So, you can wait the price of crypto recover after panic time to sell your coin.