I have never understood the "dress up" for a checkride thing. As a result, I've never done it. I think it is much more important to be comfortable. If a shirt is what adjusts your attitude then the shirt isn't the problem, it's you're attitude. I'm not recommending that anyone take a checkride in ratty jeans and a ripped shirt but anything more than a polo shirt and a nice pair of pants is over kill in my opinion. Hell, I've never even taken a ride without my hat.

To the OP it sounds to me like you're trying too hard and getting ahead of yourself. I teach my students this mantra: "Fast is slow, slow is smooth, smooth is fast". Basically if you rush through then you'll be starting again. If you take your time and do it correctly then you'll get done with time to spare and a lot less stomach acid.