There's not necessarily any harm in making a few c0ckups as well - I thought I'd made a horlicks of a couple of exercises, but still got a job offer.
One thing I would say and that is if you do make a mistake, just acknowledge it, put it behind you and drive on. If you start thinking you've blown it then the remainder of your detail will suffer as a result, and you probably will! Recover and fly a reasonably good trip for the rest of the detail, and chances are you will salvage a pass.
Make sure you learn all the pitch/power and configuration stuff for the 1-11 that they send you. I was told they are not expecting perfection, but do expect to see improvement in your handling, good CRM, and leadership from handling pilot. He also told us that you are only assessed to DA/MDA so the landing or go-around are not assessed.
Good Luck!