While feeling some discomfort is entirely normal during a deep tissue massage, it should not be causing unbearable pain. If you are experiencing pain that surpasses minor discomfort, let your massage therapist know so that they can go a little bit lighter in that spot. The point of receiving a deep tissue massage is to work on existing muscle tension, which requires manually breaking it up, which requires a fair amount of pressure from the massage therapist. The level of discomfort you feel will vary depending on how much muscle, adhesions, and scar tissue they have to break through, so if you have severe muscle tension in one spot, you will likely feel more discomfort there. If the discomfort evolves quickly into deeper pain, let your massage therapist know right away so that they can adjust accordingly.