For years, I've been nervous doing heavy squats because I'm always worried about what happens when I fail. It's not like you can drop the bar, because when there's 200 pounds on it, you have to worry about where it's going to go. Will it hit you on the back? Will it wrench your shoulders? Will it squash your knees?
It finally happened last night. I was feeling good, and thought I could go for a new PR on my squat. I did 215 for 1 rep, my previous max, and it was fairly easy. So I added 10 more pounds, strapped on my belt and couldn't get out of the hole. Fortunately, I had a spotter, and I only needed a bit of help to stand back up. Plus I always have the safety chains up when I go over 130 pounds. I really feel like I should have gotten it, but it was very close. And failing wasn't a scary, dangerous thing at all.
My back is getting fried from the heavy lifting though. I plan to do three more days of intense lifting, then take about 5 days off to let my back recuperate.