That was certainly my experience as well. When I was drinking I cycled between being exuberant/relaxed and being irritable and uptight. When I quit I initially had some bad periods of being irritable without the relief of alcohol to stuff it. However, over the weeks and months the irritability has receded. While it is based on his changing brain chemistry and you should try to be understanding, you can also call him out when it happens because he should be working on it as well. He may not be entirely aware of it when it is happening.