The problem about trying to learn and master an art is about getting carried away with it and trying to use it everywhere. We have the famous Mark Twain quote " To a man with a hammer everything looks like a nail. " Similarly with anything we know very well or anything we have learnt new, the urge is to try to apply it wherever possible and sometimes wherever its not advisable.
For a surgeon the most important thing to know is when not to operate. Similarly for us who know or are good at one discipline of investing, its very important to know its limitations. Trying to apply DCF where it is not applicable e.g in lumpy businesses or unpredictable businesses is often fatal. Similarly trying to apply patterns that work during bull markets during bear markets is likely to fail.
We have to be open to the idea of applying different disciplines of investing to the same idea. If in some idea, the charts, fundamentals, scuttlebutt etc all fall together there is higher chance of success.
Regarding drawdown in stock prices after buying I find that if stock prices go down along with general market corrections i am okay with it. Besides if the investment thesis I have in a company continues to play out I am not too worried. But if results do not come through as expected, I usually exit. Letting winners run is a thing that comes with experience.