On the subject of risk vs. reward and 'cutting losers'

Morning all. Been trying to get a handle on my risk management lately, specifically when to actually cut a loser. Everyone preaches 'cut your losers short, let your winners run,' and I get the theory. My issue is, how short is 'short'? I set my stop loss, sure, but then I'll see a bounce that would have turned it around, and my confidence takes a hit. I'm trying to figure out if I'm being too rigid, or not rigid enough. Are there any seasoned traders here who could shed some light on their process for distinguishing between a temporary pullback and a genuinely failed trade? It's that fuzzy area between 'patience' and 'stubbornness' that keeps tripping me up.