I agree its a personal thing but should be considered as an option when developing your risk management strategy within your trading plan.
Personally, I use them all the time - as soon as I buy, I set a stop loss that is calculated on the daily Average True Range x 2.5. Support levels also important to take into consideration. This works for me but as I said, it depends on your own trading style.
Best thing to do is to do some reading around risk management, select a method that fits well with you and document it in your trading plan. Then apply the strategy and see how it works for you, review and refine.
