I hate destroying hope and optimism

• A student, taking a test, asks me "Do we need more information to solve this problem?"
  
  I take a look. "No" I say, "Sorry."
  
  "That's okay, just thought I'd ask."
  
  
• A fairly hardworking student who is taking two of my upper level classes comes to speak with me. He inquires about his grade in one and is wondering how well he would have to do on the final. I tell him he has a pretty solid B, so he has some wiggle room, and that I would not expect him to fall to a C unless he did really badly.
  
  "Oh, I'm not worried about that." He says, confidently. "What do I need to get an A?"
  
  Not sure what to say in the face of such confidence, I decide to rely on simple math. We add up the points he has missed on the exams so far, note that these are the sum total he would be allowed to miss, not including points lost on homework and in lab, and he quickly sees the problem.
  
  Then he says, "Well, at least I'm not worried about physchembio classwithlotsofmath."
  
  Fortunately, in that class things are looking more positive, but not so much that he shouldn't worry.