For me, I'd been in sales for around four years and I was going through a dry patch.
Someone recommended I read a David Sandler book called 'You Can't Teach a Kid to Ride a Bicycle at a Seminar' which read more like a novel than it did a sales manual.
(The Qualified Sales Leader is the same type of book in my opinion.)
I realised that trying to be the cleverest person in the room and being overly enthusiastic about my offering was having a negative effect.
I had spent the past few years doing the show up and throw up routine. That wasn't selling!
The first time I told a prospect that I wouldn't send a proposal until we agreed what it was to include, how it would be used and what the outcomes would be felt like the scene in The Matrix where he dodges the bullets...
Without this book, I'd probably have moved into a different field and looked back bitterly on my stunted career in sales.