Have you ever bought the dip, but then the price breaks through the support and continues dropping deeper for weeks or months? 
Well, I have done it before.
Well, I have done it before.
Even the best traders make mistakes a lot of times. It's just that you make sure you have some sort of "contingency plan" if your initial plan(like buying the dip too early) doesn't go well; like having more cash ready for more dips and such.