I think this is the most important of them all you highlighted above. Having no stop loss in your trade is similar to a car not having a break to prevent an accident from occuring and you know when it does occur, it'll lead to death or injuries which the car most likely will be destroyed in the process. Now imagine similar even happening to your trading funds in the exchange.

Stop loss isn't all about preventing your from losing but can be used in securing the profits you have recorded from you previous trading hours or days. The common recommendation is from 5% to 10% and this shouldn't always be from your entering point into a trade.

You can always increase your stop loss exiting price as the trades continue so as you take profit when a sudden drop is about the occur without you been active in the market.