There are special problems with vacations. People have built up routines to manage their daily lives. These routines do not apply anymore. People are often, during vacations, forced to be together all the time, this is difficult for some people who need time to be alone. Accepting this and arranging the holidays so that people who need to be alone some hours can be this also during the vacation can be a solution.
People also sometimes have unreasonable expectations of how happy they will be together during a vacation.