Just for fun, here are some things I wish I had taken to heart, back when I was a young biblical languages student (and, really, some of this can apply to any Bible student, not just the Greek geeks).
1) Work hard. A good grade doesn't mean you've mastered it. At the same time, try to get more sleep. :) It actually helps.
2) Greek isn't everything. Neither is Hebrew. Don't get hung up on parsings and definitions unless absolutely necessary. You might find that it's more seldom than you thought.
3) Watch your pride. Who do you think you are? Pride sneaks up on the best ones, and even leaks out in a humble form. I mean, you gotta admit that you're always looking for subtle ways to impress with your language skills: Listening to someone trying to explain John 1:1 in their story of an encounter with JWs, and they obviously don't know Koine Greek. "Oh yeah, uh, I know a little bit of Greek." "REALLY? You must be so smart! Can you read fluently? Can you explain the Greek in John 1.1?! What about in John 21.15-17? " They take out their Bible, and flip to a favorite New Testament passage. "What does the Greek say here?" As though it really makes a great difference, heh heh. I know better. *Pats self on back.* Being a languages geek doesn't put you above everybody else. Stop it.
4) Just because that preacher didn't get his Greek right, does not mean his sermon has been completely spoiled. Be kind, not critical.
5) Just because that preacher didn't insert a comment about the original language into his sermon, does not make him inferior.
6) Stop stressing out about getting perfect answers 100% of the time, and enjoy the learning experience.
7) I know you hear it all the time, but seriously, if you don't practice/use Hebrew and Greek, you'll lose them. So, if you want to retain anything, practice it. Keep reading it. There are no other substitutes.