Hey there,
I have no preference on selling winners or losers - it all depends on the stock itself. I tend to have two approaches - one for my dividend/foundation stocks and another for my growth.
In terms of dividend/foundational stocks, I buy with the intention of never selling. The only time i'd consider selling a winner or loser is if my investment thesis has changed. Since good solid companies form the basis of that section of my portfolio, it is rare whereby i'll sell a position.
As for my growth, I always buy the stocks with the long-term in mind but always have a plan to recoup my capital (kind of an exit strategy). So if the stock runs up, I may chose to exit a portion of my position and hold the rest. I do this with all my growth stocks. I know this in advance of purchasing, so if the stock reacts accordingly I execute the plan. It will also vary depending on the stock. Since i invest in more speculative positions, investment thesis does change more often so I may sell a winner or loser if the reason for which i bought it changes. This happens more often in my growth portfolio and could be a winner and loser.
Case in point i ahve XBC - and the situation has changed. However, I am given them a quarter or two to see how they perform in relation to guidance. If they keep missing, I'll cut my losses (50%) and sell out. If the can hit estimates, I'm likely to keep the stock and not sell at a loss cuz i still like the industry in which they operate. They just had some very poor financial controls which need to be resolved.
Likewise, I may sell a growth position if I see a better opportunity that I don't want to pass up and I have no cash available.
Hope that helps, that is my approach - Dan's is different than mine for the growth portfolio but he can speak to that.
Mat