There is another option which is widely considered as a bad one. At the end of the test, you have an option to cancel your scores before you get the chance to see them. If you are hundred percent sure that you would score considerably lower from what you need then cancel it.
However, you should do that in a wild scenario, such as: you were attacked by a bear on your way to the test center, you randomly puked during the test, Chuck Norris gave you a visit during the test, etc. If your goal is, say, 740 points and you hypothetically score 610, it is better to see where you stand. You will probably have an idea what you will need to improve. Imagine if you scored 610 and canceled your score but thought that you were somewhere along 680...that could hurt you quite a bit. It is all bunch of buts and ifs but you get my point.
As you can see something wild has to happen in order for you to significantly under perform. Get some sleep, make a decision ASAP and stop thinking about it, otherwise it can make you very nervous during the test. Relax.
I have seen countless number of people on this forum who scored on first attempt somewhere along low 600s and made it later into the 700s and got admitted to HBS, W, or any other school. The point is, adcom does not care about your score as long as you score well eventually. Technically, you could score below 600s and still end up in the 700 but that would require quite a lot of work...at least that what experienced GMAT people from this forum are saying.
p.s. I am not telling you this from my experience but from what I have read on this forum over a long time.