I recently got a note from a student about grades; usually these sorts of communiques come later in the term, but whatever. The jist of the note was, "So if I get straight As for the next two terms, I should graduate with a 3.0!"
Of course, if it were easy for this student to get straight As, she'd be planning on graduating with a 4.0.
Usually students are working on the "in this class" model after receiving a midterm report of F for some 40% of their grade. In that case, they're usually saying, "if I get all As on the rest of the assignments, can I get a B in the class?" I usually sit down and do the math right there with them:
F (say, generously, half of full credit) for 40% of 100%=50 x.40=20.
Add to that, 100 x .6 = 60
20+60=80 and YES, it's mathematically possible to get a B-!
BUT, since you've never gotten a single A on an assignment yet, what makes you think you can pull straight As? (I do try to say that with reasonable compassion.)
One time, I've been totally surprised by this type conversation: My advisee had come in to talk early during the semester. She was taking 16 credits, and figuring out how long it would take her to graduate. She figured out loud, "if I finish 16 credits a term, I can graduate in 2 terms."
I gently pointed out that she'd never managed to pass more than 12 credits in any term, and asked her why that would change, and even that wasn't a sure thing.
And her answer convinced me: "It's changed because I went through rehab and I'm not drinking anymore."
You know what? She was right! She did graduate according to her plans, and with a much improved grade point average. I loved that surprise.
UPDATE on the blood thing!
Apparently, yes, I had some. And it's red despite my being an alien.
Iron: good to go!
Blood pressure: sleepy mode
How tough are my veins? I made the Red Cross nurse cuss. Yes, I made her cuss. She stuck in the needle, took off the clamp thing, and got nothing. Then she cussed and dug around until she found something. That was less fun than it sounds.