Students are expected to observe the laws of the country they are in, as well as societal norms. If you have simply agreed to be present in a particular setting for a certain length of time, even that constitutes an agreement. You cannot then arbitrarily decide to leave before the appointed term is completed. Obligations must be met. Study abroad is stressful regardless of how prepared you consider yourself to be.
Careful preparation can help overcome some of the stresses.
However, students who have a history of substance abuse should talk with a physician or advisor before making the decision to participate in this program abroad. In many countries, illicit and illegal drugs are readily available and alcohol may be easily obtained. In some countries just having alcohol in one's possession is illegal. Being away from familiar surroundings can trigger use of drugs and alcohol. Adherence to the law and good judgement about appropriate behaviour within the law are both absolutely essential.