I had to. I couldn't walk into another office and see the salespeople sitting on their rears trying t make a deal happen. It's one of the easiest fixes on a sales floor, and it makes a huge difference. Prospects can tell the difference in your energy, on the phone, when you are sitting and standing. I know Tony Robbins talks a lot about this too in his training, but more so on a personal level. If you are depressed, stressed, worried, or worn out, change your physical attributes first. Then your mental game will follow.