Partnering with your therapist
Communicating with your therapist is vital.  Share with them your goals for the work.  During the session, let your therapist know if the pressure, your position or anything else is uncomfortable.  Also advise them of any injuries, surgeries or medical conditions you have or medications you are taking.  If you have a recent injury, your therapist may advise you to consult with your primary health practitioner before proceeding with myofascial release.
Multiple sessions often increase the effectiveness of myofascial release.  You and your therapist can work together to determine session number and frequency.