I am a lefty too, and after trying all through my teens and early twenties, I finally figured out how to knit just after my 26th bithday.. with KH's videos. They are the ONLY thing that has ever worked for me..because everyone who tried to show me was either right handed, or were left handed, but just didn't knit that well themselves- so couldn't show me.
I think with knitting, it still manages to work out okay for a lefty to knit like a right handed person would- because you have to use both hands no matter what. But then, I am a yarn "thrower" or "wrapper" because my right hand isn't able to hold the yarn the way Amy does with her fingers of her right hand.
It's just another thing that we have to adapt to as lefties! lol