It takes just one trader.

Once upon a time (not too long ago), a prominent floor trader decided that the wanted to get off the floor and start trading on screen.  In the pits, he had no need for technical analysis as he was trading order flow and doing it very successfully.   He realized that he would need to learn something about technical analysis. So he got put in contact with the young hot shot technician.

The young technician was eager to show off his knowledge and the two men started watching the soybean market together.  The technician was calling out support and resistance points and the market gradually drifted to a support point and the technician proudly boasted this will be the low for the day.  T

he floor trader looked over and asked "are you sure?"

The young technician responded "absolutely"

"Bull shit" said the floor trader with a knowing  look on his face.

The floor trader then got on his phone dialed his broker and said "sell 2 million soybeans"

 The market then then ripped through the "support" proceeding to drop lower and lower as stops were triggered.

The point is that no matter what your conviction in a trade or how many times the pattern or trade has worked in the past, it takes just a single trader who disagrees with you to destroy your chance of a successful trade.  For that reason we must plan for the downside of a trade, understand the real risk we are taking,and accept that risk when we put the trade on because there are no sure trades.