The first is a more honest state when drunk. The person will be more apt to call their ex and beg to get back together, or they may tell them off. Its a mix of emotions that leads a drunk individual to feel as though they have made progress when in the morning they will realize that there were consequences for those words.
The second path is a "free" state. The drunk person will feel as though the only way to get over their ex is by having a great time and by showing him/her that they can have fun without the other's company. This leads the upset individual to do one or more of the following: get blackout drunk, get sick, be a social butterfly: being either creepy or smooth )creepy leads to fights; smooth leads to intimate activities), and having the confidence to venture outside of the party atmosphere (public places have cops...). All of these actions have consequences that must be dealt with if not at that time in the morning.
None of these actions nor consequences are what were desired in the beginning. The purpose of the person's drinking was to get rid of a specific emotion. Whether the emotion began to go away or not doesn't matter. If it did the person drinks more in order to keep up the effect. If it did not, the person drinks more in order to get it to. Both of these paths lead to consequences that will lead to regret. Drinking with one's emotions never turns out the way it was meant to. It doesn't work. If you are going to drink there cannot be a hidden agenda. And usually if this is a true a person will drink less and come out in the end with a positive experience.