Quitting smoking, feeling low
Have you tried chanting Hare Krishna? Some people get enough spiritual strength simply by doing that to stop smoking.
If you follow the links on the "About Krishna" pages on Krishna.com, that will help you get a better understanding of Krishna consciousness. You should also read Bhagavad-gita at some point, but Science of Self-Realization and Isopanisad may be easier to begin with.
Two ways to become inspired to chant are 1) Force yourself to chant every day; you'll gradually become purified and start to like it. 2) Find some way to serve and glorify devotees who like to chant. If there's a Hare Krishna temple near you you can go there when you have free time, and ask what you can do to help.
Krishna is willing to accept people who never stop trying to attain His mercy, no matter what their previous position, as we are all His children.