Dilemma is a situation where it is difficult to take a decision out of the available alternatives. The reason might be both the choices are favorable or undesirable.
When a stimulus triggers an obsession in an OCD sufferer, the obsession creates anxiety, fear which force the person to perform certain illogical, irrational rituals. Completing such rituals (compulsions ) brings momentary happiness or false relief. While performing the ritual a part of person’s mind keeps telling him those acts of compulsion are silly, irrational and doesn’t make any sense. Counter to this argument, the OCD part of the mind threatens him to complete the rituals, otherwise some thing evil would happen. These threats cause discomfort.