I haven't made any really big projects, but I had to frog an entire hat after I was a few rows into the decreases because I noticed a wrong cable cross down near the beginning. I learned from that to check my work a lot more often and more carefully!
My most recent thing is a lace shawl. I'm not 16 rows into it, but I've probably knit about 40 or more rows, and have started completely over 3 times. Yes, I used lifelines, but still messed up...I found a dropped stitch below a lifeline!
It's going smoothly now,though.