For many people, smoking and drinking alcohol go together. There are some physiological and behavioural reasons why they are related. Therefore, a common reason for starting to smoke again is the use of alcohol.
You may want to limit your alcohol use in the early days and weeks after quitting. If alcohol is a strong trigger for you to smoke, don't drink alcohol at all for the first month after quitting.
If you have or ever had a drinking problem, it is okay to try to quit smoking -- even if you are trying to quit drinking at the same time. It isn't easy to do, but it may even help your recovery, and it will help your health.