I've been knitting for over 20 years and I still feel like such a newbie sometimes, and then others I feel the stuff is old hat.
I will be honest, my toughest project so far was the Tree of Life Baby Afghan from Lion Brand. It required strict attention to detail and taught me a lot about my knitting. Doing some lace afterward helped my confidence level as well.
I'm not exactly the brightest bulb in the chandelier sometimes, and it takes me getting over my fear of some technique or just practicing it over and over until I feel confident enough to attempt it on my project. I have swatches all over my desk from testing needles, gauge, stitch patterns (I hate double seed stitch).
I will admit, this site renewed my interest in knitting and helped me open my horizons quite a bit. I'm no longer knitting the square items. I can increase, decrease, make my stitches do things that make pretty designs. So I would have to say, this site, the forums, the videos, the glossary and everyone here has really helped me get to where I am now.
Knitting to keep my sanity. It's working... kinda...
OTN: Dr Watson's Cable Crew Neck
OTN: Writer's Cardigan