My take: stop-losses are an essential discipline. Trailing a stop so that you raise it if the stock goes up, to lock in some of the profit is even better. You can split eg bought at $3.30, price moves up 10% - raise stop for 50% of position etc. tricky to get the distance right - too close and you get stopped out when the trend hasn't changed; too far and you give back too much money. Some will sell part of a position on upwards euphoric extensions, hoping to buy back on retracements. And the %s can reasonably change too - tight stops initially and then wider as more profit is made.
Those are general trading rules / tactics but more generally, I like PPH a lot - big market and apparently good management. However, the change in volatility in global markets has reduced my risk appetite, so I sold a good portion of my holding yesterday. Despite any fundamentals, the price could be driven lower, back to $3.30 or $2.40 area quite quickly if things continued to go badly globally. (Previous Dow dips have been shrugged off by the local market but the global nature of the reaction to this move, concerns me). If that happens, it can be very quick and difficult to get out of a position. Spreads widen and the pain and reluctance to enfore a stop-loss can be harsh (or an auto-stop-loss can get really bad execution).
And I think this guy makes sense generally:
https://www.marketwatch.com/story/the-chart-reader-who-called-this-stock-market-selloff-says-its-not-over-yet-2018-02-07-1210308
With regard to PPH - seems like we have a lot of speculative bulls in this stock and they've mostly been very quiet the last few days (including me!) which is not a good sign. I hope I'm wrong and if I'm right, I can still see PPH at higher levels in a year from. Is bit it may be painful in the meantime. It is horrible watching counted profit leech away in a grinding, drawn-out correction. I've been there.
Good luck.