Cheating is a very stressful thing to maintain. While dealing with the pressures of a new lover wanting to get more attention, there is the constant feeling of guilt that comes up when they are home. They also may be dealing with the stresses of work, the fear of being caught, and a feeling of resentment towards you. This can result in mood swings and emotional responses that don’t seem appropriate for the situation. On their own, mood swings are not a good indicator of cheating, but they often accompany the other signs.