I've been dealing with a cannabis addiction and have found that getting the right nutrients is key to feeling good while sober. People often mention it but I severely underestimated the effect that eating the right things can have on my mood. Make sure you're getting all of the essential vitamins, minerals and amino acids. They make a hell of a difference.
Amino acids are very effective at treating symptoms of anxiety and depression. For depression, supplement with L-Tyrosine and DL-Phenyalanine. For anxiety, L-Glutamate, L-Tryptophan, 5-HTP and GABA work wonders.
Rhodiola Rosea is very effective for depression.
Lecithin, or any other source of choline, is good for helping keep the mind sharp. Combined with nootropics like Piracetam, your memory will be at the level it was when you were 16.
Cutting out simple carbs tends to stabalize mood by mitigating blood sugar spikes.
I strongly suspect that addiction has it's roots in malnutrition. It also seems that malnutrition is not limited to the third world and is endemic in western society. For example, most people are deficient in magnesium, in particular drinkers and smokers, which is funny considering how rich and "well fed" we are.
The other thing that's going to change your life is exercise. It has a host of benefits including reducing cortisol (stress hormone), increasing DHEA (associated with longetivity), releasing endorphines (endorphine means endogenous morphine - free drugs with no side effects!), and probably a bunch more things I don't know about.
The body and mind are not seperate, they are different aspects of one system. A healthy body will always yield a healthy mind.
If you're still in the throes of addiction and can't see a way out, address your nutrition first - it will be considerably easier from there.