I've been strength training off and on over the years. Because of bad information about squats being bad for the knees, I never started squatting until a few months ago.
Over time I think lifters develop some mental toughness for training, so that going to failure isn't even unpleasant.
However, I have to say the squats seem different in that regard to me. They just seem "hard". I have even failed on the first rep of a first set of 5x5 that I was able to complete fully after getting more psyched up.
I used to think dead lifts were tough, they seem ok now.
Do squats get easier after a while?