Sometimes you psyche yourself out by concentrating too much on your rep. This is where speed work comes in. I do mine on on DE leg day, but any day not Max Effort day is OK. Just put about 60% of your one-rep max on the bar and do about 6-8 single lifts spaced 10 seconds apart. Nows the time to concentrate on your form so that you become sure of yourself and develop power. When your ready for your new PR, you've already had enough practice so just load the bar up, step in let your body take over- or as Arnold called it- your muscle memory. The sticky on The Deadlift in the Powerlifting forum is a good read, well worth your time. Good luck with your goals.