Such a hard topic to answer to without knowing whether you are an investor or a trader. As an investor, buy major dips into companies you believe will be there within next 10 years. As a trader I don’t give a shit about fundamentals 10q, 10k, I read price action and do technical analysis of the chart. But I’m usually in and out of a trade within minutes. I also have mental stop losses as bone mentioned, if you have a stop loss in play the market makers see the order book, tank the price of that stock to pick up your stop loss shares and move price back up.... seen it many times.... just adding my .02 cents