I agree, quitting does not ensure happiness. Then again, what does? It did clear the way for me to take the steps needed to improve the quality of my life. Of course, those efforts could come to nothing. Happiness is so fragile, so contingent. I'm human, I can and will make mistakes. Bad things can and will happen to me—things over which I have no control.
The only thing I can control is how I respond to the world around me. And because I'm not drinking, I can at least deal with people and situations in an honorable way. Honor is so underrated, especially compared to happiness. Nothing can take honor away from me unless I let it. That's something I like to think I recovered as a direct result of quitting.