An experienced trader can of course predict the market price where the altcoin price will go up and down so he doesn't need to linger long in front of their computer, because there are many things that must be done out there. And when trading is done in a hurry, they are sure will lose
Any experienced trader will have an estimated target and a belief how the market would perform and then make their decisions accordingly. There are times when you mess up but in trading when you panic and make decisions without accessing the situation, the loss will be huge. So always make your calculations accordingly according ti the market situation.