Everything is possible in a short-term. Within only one day Stock price can drop or rise even 10%. Such sudden moves are hard to predict and use to benefit for most non-intraday traders. However, statistically for some periods in a well-balanced environment, the Principle “trend is your friend” may work well, especially, in a pure Bull or Bear Market. The chart below shows that this principle is right in 5 of 6 cases for relatively small periods:



If we consider bigger periods, the trend principle may work with ratio 1:1 – in other words, no benefit of using it. This is what we had for the last one-and-half decade for the stock market. The chart below looks similar to S&P-500 index for period from 1997 to 2010. Evidently, a multi-year green uptrend changes to a red downtrend and then vise versa: