Personally I find alcohol can be a good tool and helpful during the design process.
I have had many inspirations and exciting new thoughts while relaxing with a six pack or a bottle of wine as the day diminishes. I also find inspiration while enjoying a good cup of coffee at dawn.
Sometimes I can be over inspired and forget what time it is....but that is rare, as I usually have to integrate my schedule with others.
There are times during construction that the atmosphere is not always the best for contemplation, especially when things are really happening, and many people and pieces of equipment are dependant on you for design direction.
My preference is to spend the twilight or evening hours, after all others have left, wandering the site, checking what has happened and getting ready for what is coming next....and basically grading my paper. Security is alerted early on that they will probably see me, or my truck or ATV at all hours of the night.....I have spent many an overnight on many projects, as I can sleep quite comfortably in the front seat of a pickup.
And most of the time I have some form of alcohol with me ...and I feel it has some benefit as a design tool in these situations.
On another level I have found that alcohol can also promote a beneficial relationship with certain clients...so I guess in that sense it is a social design tool as well.
But to each his own....and, as in most things, moderation is usually the best course. [on or off the course, of course].