I watched a World's Fastest Knitter video a few years ago. I think it was sponsored on the Knit Picks website, but never mind that.
After watching this incredible woman, I tried an experiment:
1) I started a garter stitch swatch.
2) I set a timer.
3) Using my normal knitting speed, I knit X rows (cant' remember)
$) Then, I knit the same number of rows going as fast as I could. Really really fast. Oh, blazing!
The outcome of the experiment: I knit slower when I was trying to knit fast.
I tried that darn experiment over and over.
I could not increase my speed when I was trying
to increase my speed.
The final analysis: The timer put me under such stress, I couldn't perform as well.
Back to knitting my usual way. Not fast, not slow. Accurately and with pleasure.