The thing people seem to not understand is that you need to keep the difficulty of the questions in mind when evaluating how well you did. If a question was extremely difficult, you shouldn't feel too bad about getting it wrong because everyone else probably did too.
The reason people feel bad and then get 520+ is that they are used to being confident and answering every question correctly. Now all of a sudden the test is more difficult, but they expect to still be able to get every question so they feel bad. Don't get hung up on the impossible questions. Be worried if you miss a lot of easy/medium questions you "should" have been able to get.
I walked out of my test feeling like I did about as well as I could have hoped for - I got all the questions I would expect myself to be able to get, and who cares about the extremely difficult questions. Ended up with a 519 (scored aamc = 516). My friend felt terrible, considered voiding... Ended up with a 524