Don't feel like a loser, that actually makes it worse! I just quit (16 days ago) after 30 years, too. I tried dozens of times before to no avail. For the last few years I actually managed to get myself addicted to both cigarettes and nicotine gum, lol. I don't know why it's different this time, but it is, I can feel it. I'm doing wellbutrin, too, but I'm doing the XL which is time release, don't know if that made a difference but it might have.
I do know for sure that it wasn't until I was able to stop beating myself up for smoking that I was able to quit. Forgive yourself, and focus on the positive only - you went 21 hours without a cigarette, be proud of that. The more you forgive yourself and be gentle with yourself the easier you'll find it to let the cigarettes go for good. Good luck!