We all learned that when we took a position – either long or short – that we better be able to jump out if the trade was not going our way. Many of my friends were scalpers. That means they were trading for just a few ticks and every night went home flat. Flat is no positions at all.
Be wrong and run home with most of your money. You still have enough to invest in a better opportunity. If you are disciplined to get out of any bad situation early you will end up a rich person.
I don’t care what business you are in you don’t put your whole wad on a single outcome and stick with it until it either works or go broke. That is what brokers and mutual fund managers want you to do. They want you to buy, but never sell.