I like reading the advice in this thread, but I feel like people use the same word to mean different things.
For instance "failure". I remember reading something Arnold wrote in his encyclopedia along the lines of: "Many trainers tell me they cant squat another rep, but I force them to and guess what, they always can!"
I took this sentence very seriously and would take my squat sets to excruciating extremes. I would feel terrified of doing another rep, but I always forced myself to get one or two more... and then another one or two, until I couldn't even do a rep with bad form and collapsed onto the pins. This is what I think of when I think of going to failure.
And now people will probably say, "well of course stupid, you broke form to get those extra reps." But doesn't everyone? After all, if you absolutely refuse to budge on form at all, going "to failure" is actually pretty easy. Where do you draw the line on this? Do you go all out, and do anything to get the extra reps? Do you stop as soon as you can't accelerate the weight perfectly smoothly? Or somewhere in between?
The more I watch professional bbers actual training vids (not the DVD performances) and pay attention to these things, the more it seems like they stop almost just as soon as the going gets a little tough. If this is "failure" then I had quite the wrong impression for many years...