Let's compare how you prep for both and how you conduct yourself during & after.
To prep, you:
Pick out a great outfit; something impressive, yet not too over-the-top.
Get anal-retentive with your personal grooming.
Rehearse a few things you'll say without sounding too rehearsed.
While you're there, you:
Make sure you are engaging, witty, yet slightly restrained.
Show interest in what the other has to say.
Try not to appear desperate; they can smell that from a mile away, and when they do, you're done for.
When it's ending, you:
Calmly and without desperation, express your interest in moving forward with things.
Affirm to the other party that you look forward to hearing from them.
When you're back home, you:
Run the whole darn thing through your head and hope you didn't eff-up something or come across as a completely desperate fool.
Try to stay calm and hope you'll receive a positive reply from them soon, or you want to follow up with them but don't want to seem desperate.
So....what's the point of this comparison?
If you're searching for work and following interviews find yourself feeling frustrated, puzzled, dejected, rejected, or defeated, try and give yourself the same advice you would if that were a date you just had: