Part of me likes to think, when you make major decisions while completely mashed but still functional; it's your subconscious playing the bigger role in your decision making, which can be good. Compared to stone cold sober decisions made when you're completely self-conscious.
For example, your self-conscious self may to be too pussy to make decisions that would be in your best interest long term, but are more cozy short term. Like breaking up with a controlling GF, or deciding to finally stop taking shit from someone, fear of success/failure decisions etc.. They don't call it liquid courage for nothing..
But if too fucked up, your id takes control over your super-ego and you do things like quit your job because it's a beautiful day and you don't want to go in.