No. If you expect the unexpected than it is no longer the unexpected so you know not to expect it which means you dont expect it so you cant expect the unexpected.
The first appearance of the quote is by Heraclitus (c.535 BC - 475 BC): "If you do not expect the unexpected, you will not find it; for it is hard to be sought out, and difficult". Oscar Wilde...
Not sure, could be something from a science-fiction, suspense, or Occult drama, all which deal with unexpected plot twists or subjects. a milder of more user-friendly ( not so blunt, as that quote...
If you are referring to "nervous" as anxious, then it is definitely when it is expected beforehand. Anxiety develops in a mind that has already thought over consequences of actions or events that...