For a lot of people Christmas spirit means the alcoholic rather than mental kind. Like a car without petrol, Yule without boozy fuel just won't leap into action.
Alcohol does have some benefits.
It can certainly relax people, while small amounts of alcohol stimulate the production of important digestive hormones such as gastrin, and increase liver blood flow, both of which can help with the digestion and absorption of the Christmas feast. But it can also ruin a good time. Too much alcohol can almost totally inhibit stomach emptying, causing very unpleasant distension of the stomach and extreme indigestion. It also destroys inhibitions so that you are more likely to tell miserable old uncle Alf just what you really think of him, while many of us know only too well the misery of a bad hangover. This takes the edge off hunger and helps to line the stomach.