I am starting trading some month ago.Bought some alta coin but now all alta coin are down and i donot understad what can i do?I get a big lose if i sell this.So how control my mind ? 
you should practice self disipline , the moment you but an altcoin profit is what is in your mind right ? if you sell your coins right now would you think you could get profit ? obviously no ! so the best advice I can give you is dont ever sell if you are not gaining profit jusy Hold it it will never be always down surely it's value will rise just wait for it The problem with altcoins is a few thousand dollars can literally change the entire market. If you invest too much, a single dumper could ruin everything for you. Look at what happened with eBTC recently. Someone dumped like mad and the price crashed ~80% within an hour.