Even if "do what makes you happy" were the best rationality advice, the big problem is figuring out what actually makes you happy, how to achieve it, and how to maintain/improve it. Getting drunk is pretty bad advice for a rationality standpoint, because it's sacrificing long term gain for short term pleasure, which is basically the opposite of what you should do. The man drinking at a bar all day is happier right now than the one working extra hours or studying, but in a few years, their happiness will probably be reversed as the latter's investment pays off and the former is still just drinking (only with more health problems).