I bought my first shares in 1974 and have obviously been in the market for some time....(More actively in the last five or so years)..Only this week I have actually realised that you must NEVER TRY INVESTING OR TRADING AGAINST THE TREND. Never try catching bottoms. (Rather just tickle them, or pinch them or just look at them).
If a share price is trending downwards do not be tempted to buy it because you think that it cannot fall further. (Its called trying to catch falling knives). It is now my firm rule that I will only consider buying after an uptrend is confirmed. I will also only sell once a down trend is confirmed.