It's important to talk to your partner about what if one is successful and the other isn't or just isn't motivated to quit. One common feature of everyone who relapses is that cigarettes are readily available and if you live with a smoker, a pack is always right there. A discussion might include how the smoker can still be supportive of the other's attempt to become smoke-free. What mutual boundaries can be established? As much as the quitter wants the other to join them in being smoke-free, it is a very individual choice and you can't force someone to be in a different step in the process than where they are.
Sue decided to quit for herself and came to the cessation classes alone. After quitting, she would sit each evening with her husband Bill and watch TV, while he smoked. While being around Bill as he smoked was tempting, Sue was determined to stay smoke-free and did not say anything at all to him about his smoking. After six months, Bill decided if his wife could quit and not say anything, he could quit too. Sue came with Bill as a support person to the cessation classes.
Marcia's husband decided at the last minute to not attend the stop smoking workshop and quit along with Marcia. She was OK with that but after she quit, he would blow smoke into her face. She realized that not only was he not supportive of her becoming smoke-free, he wasn't supportive in any area of her life.
There is no right answer, only what is best for each couple. The key ingredient is communication. Talk to each other while you're still smoking. Becoming smoke-free can change the dynamics of the relationship. How can you support each other regardless of the other's smoking status? If you've both smoked inside the house, will that continue or will there now be smoking areas? If the non-smoker has a weak moment, what can their partner do besides giving them a cigarette?