The injured brain never fully recovers. It can recover to a fully "functional" condition but it will be intolerant of stresses, whether they are emotional, physical, or chemical. Alcohol is a definite chemical stressor.

The researchers used to say abstain from alcohol completely. In the recent years, they have suggested that a single serving per day is OK and may even be beneficial. The relaxation that can come from a single serving can be valuable to the brain. If one does not have other ways to relax, the single serving is likely OK.

You will need to remember that just because the noticeable symptoms are gone, that does not mean the brain has healed to a condition like it was pre-concussion. Once concussed, always concussed. Treat your brain with this in mind and you can lead a long full life.