Markets never go in a straight line, in either direction. One question then that a trader has to ask is at what level to expect a retracement, aka a pullback. Failing to account for retracement can either result in missing out on profits, by exiting the trade too soon.
Understanding how trends form is obviously vital if you want to time entry and exit points for buying and selling. This makes Elliott theory an interesting model.
One of the ways to succeed in trading is to predict the market by thinking “ahead of the crowd”. When doing this an uptrend can mean a selling opportunity. A downtrend can mean a buying opportunity.