Seriously, you don't have to worry about the comeback part. If
you're willing to work hard, doors will be open to you.
I flunked my sec3 exams pretty well. As in, I got distinctions,
just from the wrong end. I fell one level or whatever you call it,
from Express to NA. The thing is I never stopped believing in
myself. I worked hard and never stopped chasing my dream, even when
others felt it wasn't possible.
Now, I'm in uni reading law. If you asked me then if I could see
myself being where I am now, I doubt I'd say yes. I'd wish, and I'd
pray, but nothing more than that.
I'm not the only one who flunked once, and during a semi-crucial
time, and came back from it. Plenty of others have, and you don't
have to worry. As long as you're willing to work hard, you'll get
there.