You can both do this; you've done it before and you can do it again. Addictions are tough to kick and you both may benefit from some self-help books on overcoming addictions.
Coming to the decision to quit is the first step, but support is also important.
Find someone to whom you can be accountable, preferably a person who you can meet with face to face as well as finding support online. The single most important thing that helped me quit and still helps me stay quit was getting it through my thick skull that it was not my love for smoking that kept me smoking, it was my addiction to nicotine and when push came to shove, I could not name one single thing that I honesty liked about smoking other than making the craving for nicotine go away for a while.
All the other times I tried to quit, I had done it with the mindset of having to give up something I liked and enjoyed and thinking like that kept leading me right back to it even though I knew that it was hurting my health.
Keep quitting until the quit sticks.