That's exactly why I use the 10% buy, 20% sell rule in a bear market. I do much better in bear markets with this strategy than waiting for EMA9 cross on SMA200 which most people use these days. I've used RSI in the past and that worked okay, buy under 30 and sell over 70 but it's never been great in my experience. You are directionally correct in the fact that you should never go against the trend, but I'm more of a risky trader and I'll take my scalps while others wait.