I've actually got the same tooth to do a practical on in a few weeks - my professor's suggestion to avoid failure: place a folded matrix band between 30 and 29 so you don't ding the next tooth. I realize you shouldn't be hitting anyways, but no sense risking total failure when you're that nervous. Also, I find that the eggshell approach, where you cut almost all the way to the mesial, but leave just a tiny shell of tooth structure left, which you can break of with a hatchet when you're just about to be done, is a great way to do it. I use a 254 or a 330 usually.
PS. And you're saying they don't let you buy extra teeth to practice on?