It's okay, you managed 4 hours without smoking and you only smoked 1/2
My last smoke was at 9:00am - it tasted horrible but I couldn't resist and I to only smoked about half before dousing it with water and throwing the pack away.
Don't let it get you down, you can do this but it will be the hardest thing you've every done but we're all here to help you and can all relate to how you're feeling.