The Big Picture details the importance of understanding the difference between a "real thing" (i.e. market bottom) and a bear market rally. Here is point #1 of 3:
Follow the Playbook: The smart investor’s playbook is very different in bear markets than bull markets. In a Bull Market, you buy the dips. Lower prices are an opportunity to buy into equities at cheaper valuations. Most sales are disappointing, as prices eventually go higher. Buy & hold is the simplest, most cost effective investment strategy.
Bear markets call for a very different set of plays: You sell the rallies; higher prices are opportunities to sell equities at premium valuations. Most buys are disappointing, as prices eventually go lower. Buy & hold is a losing strategy – trading what the market presents to you is the best risk management strategy.
The goal during bull markets is to grow your capital; the goal during bear markets is to protect your capital.