No, it isn't. However, in order to maximize your chances of winning the trade, you must use the volume indicator as your confluence. Some individuals use numerous indicators such as EMA and RSI in addition with a bear flag pattern. The more confluences the higher the probability. If you see a bear flag, you can utilize the EMA as dynamic resistance and the RSI for divergence. If you find these all in the chart, it raises your chances of winning the trade.