I agree with Sean on this. You also have to take the end of what he is saying as 90%+ of the tactic. For example, in our bids and in our presentation (which has become very useful) we don't necessarily say word for word "we are the best" but we do say things that do more than hint. Some of my presentation seems kind of snotty and "big shot" but it also explains why I have the attitude I have and it is a perfect jumble of words if you ask me. Then I'll go on to literally show my potential clients the actual difference between our work and their work. This is where I am very careful.
Over the last two years I have been developing ways to make my business run more like a machine. It is in this process that I can feel confident to send any potential client to any property at any given time for a reference and I know they will be impressed with what they see. This is a result however, of pretty much mind raping my clients in to the best service I offer. We stress weedless properties and guess what, our properties are weedless. We stress 0 irrigation issues because of how dedicated our techs are and guess what, we have 0 irrigation issues.
My point is this, if Sean is telling you to say your the best and you're not reading the part where he is telling you to also be the best, then you likely don't know how to be the best and you should learn or just do it. It can be tricky at first but you soon realize that it is a necessity. It's called putting your money where your mouth is.