There has been much disparagement of the stop-loss. I have never left one with a broker but I have occasionally found a mentally-held or ‘note on my desktop’ useful, even essential. This has nothing to do with NKTR, extreme drops are in practise rare.
Let’s say you have an investment in a company you have decided to sell. The stock price is cheerfully going up. Why would you pre-empt the situation and sell now? ‘Never interrupt your enemy when he is making a mistake.’ (cannot remember which general to attribute that to.) In addition, the market is in reasonably confident mood. So I would make a desktop note of any new high and the price at a (probably small) % down from that I would immediately sell. That might go on for some time.
Sometimes a small and speculative holding bought on an acceptable valuation morphs into a total craze de jour with a wide-eyed fan-club and ridiculous momentum. I recall that happening with 3-D printing. I rode this absurdly exciting horse right to the end of the race, able to do that only owing to deep cynicism, knowing I was going to sell out and the note on my desk.
Everything others have said above is true but the mentally-held or desk-top version can come in handy at times.