Mental Block, Hills and more Hills

What kind of gearing do you have on your bike? Consider getting a different cassette which makes climbing the hills easier. New cassette if you get 105 may be $55-65.

You might consider a 12-27 as an option. I have 4 different cassettes that I use for different courses. My goal is to make the course feel flat (I know not really possible) so I can use easier gear to make my effort be more consistent.

I'd get a new cassette then go out and ride the course so you feel confident about your ability to get up the hills. I was there with you...my first really hilly tri I had to walk up 4 hills..hated it. Next year I made it up and the third year I had taken almost 30' off my bike time..went from 13 mph to 18mph.

Don't discount the effect of not having fresh legs.  At my first Oly last year (Mosseman in NH), I went out to ride the course the day after flying across the country, and the course seemed brutal.  Two days later, after some R&R, and with the excitement of the race, I loved the course and had an absolute blast.

However, if you are slowing to the point of dismounting, I agree with the others and would consider changing cassettes to give you another gear to get you over that hill.