Gator -
With where you're at in your 5x5 for deads, 300x1 should be simple for you. I have to believe that a big part of your deadlifting woes is your mind. Ever since I started reading your posts about your deads, you always make a point to say how bad you are at them.
Time for some tough love, Buddy.
ENOUGH. You're not bad at deadlifting, Gator, so knock it off. 300 is chump change for you and you need to BELIEVE that. You have been progressing since you started this HST thing, so there is no reason for you to feel bad about where you are - unless that's what you are telling yourself. You're going to nail 300, then 350, then 400 - all in time. You don't suck at something just because it takes a while for you to get where you want to go. SO - KNOCK IT OFF ALREADY.
Don't you dare think I'm trying to be mean here - I'm just trying to get you out of this funk. And yes, it is a funk.