It is not some sought of prediction but the sign of a good businessman is that he will have insight about the possible rise in the portfolio in a particular interval of time given good market condition so it should not be based on arbitrary numbers.
I like that! Sight of a good businessman!! Simply put, when you approach trading like a business, you will tend to know what to always do at every point in time without any form of emotion. Yet, people also need to learn that it is not all about stop loss alone; it is about know where you actually want to be placing that stop loss which would basically be part of your strategy as you are buying and selling and in most cases, your loss should never be more than your potential profit.
I know a lot of people tend to be a whole lot skeptical when it comes to the use of stop loss, but in the real sense, without it, you are easily going to be screwed.
Stop loss is an integral part of every trade and if you miss to plan it quickly, then the chances of getting liquidated like this will always be there. In fact, the best is to always plan your loss before you entry, as that would give you the chance to analyze your own trade before even making it. Usually, with a good stop loss, and a good plan which in this case, for you to have gotten liquidated, you are simply on the marginal path, so in this case, I would say, you would not have gotten liquidated if you had the right plan with your stop loss.