It has been my experience that it is pointless to try and talk rationally with someone under the influence. The best time to talk to them is when they are sober, can rationalize, and have hopefully reached a bottom.
This concept applies to other aspects of life as well. For example, people who are going through traumatic life circumstances, such as divorce, can be in a heightened state of emotion. In this state, people are apt to make decisions based on emotion, and are not able to detach and make unemotional decisions when they are most needed. Similar to the concept of not approaching an alcoholic in the middle of a spree, we should be careful to not give life-changing advice to someone who is in the middle of an emotional breakup. There will be time for advice, but after the wave of emotion has passed. In the beginning, it is best to listen, let them vent, and allow the person to come back to a level emotional state. Be available to provide resources but avoid encouraging rash decisions.