by the time you do that, the window of opportunity might have closed already.

all the above articles are kinda right, but you only realised that after you've bought/sold the stock...which is kinda late, and you'll keep on repeating the mistake until you get some discipline, and this time to learn varies from person to person. For me, I'm still learning to be disciplined, and have made countless mistakes.

Also, general advice of buy low sell high raises too many questions already like what is low, what is high, how to determine low, high, etc?

So the simplest advice that works is to minimise losses in whatever stock you decided in buying, i.e. always set how much you're ready to lose before buying, can be in %, can be in dollars or cents, it all just depends on your risk appetite.