As an avid angler, whether fly fishing or other freshwater fishing you can pay thousands of dollars for good quality rods, reels and tackle. At the end of the day, as any angler will admit it is sometimes the knot you tied that will determine whether or not you go home with a fish.
It doesn't matter what skill level you have attained, how you tie your flies, or how much you paid for your equipment, if your knot fails you don't land your fish!