Possibly the most common mistake I see when deadlifts get heavy is the bar drifting away from the body.
Many lifters assume that a deadlift is just picking the bar straight up, but this isn't effective. As you pile on the plates, you need to think about actively engaging the lats and pulling the bar back into your body so that your weight shifts backward slightly.
Keeping the bar in tight helps ensure every pull is smooth and efficient.
There are times when the world is against you, when you girlfriend left you, your momma don't love you, and even your dog don't much care for you. That's when it's time for the mental therapy that only a brutal training session can provide.