This picture is a little dated, but the feeling is one I can certainly relate to.
Ever been so tired that your head starts nodding and you fall asleep right there in English class?
Once you finally wake up, you're happy to find your face is all wet with the slobber that only a good afternoon nap can provide.
Then, like you need this, somebody shouts, "Hey, look at that doofus!" and everyone turns to look just as you're wiping away that nasty, slimy stuff from your cheek. All you can muster is, "huh?"
After everyone has a good laugh (you're welcome), you notice that the girl you wanted to ask to the dance was sitting right next to you and you can faintly hear her say, "That's nasty" as she walks away, shaking her head.
.....Wait, I think this was supposed to be about my daughter. Whoa, flashback.