That is all very true, but the problem is that it's way easier said than done. Even if you know how you're supposed to think, it doesn't work.
I used to have no confidence at all. I never really knew why. I was never fat, i look really good (sorry for being vein) if i'd think or look at myself from the side i always knew i was smart and good looking. But i just couldn't bring myself to really feel that. At some point around the age of 30 i started to realize those bad feelings were gone. I started to feel so good and automatically my life approved. I found a great woman who i could never get before even though i looked the same and had the same job. It's amazing! I ave no idea why and how it happened. But i really hope it will happen to each and every one of us :)