For most of us, our body is in a constant state of tug-of-war with itself, as muscles use tension to counterbalance other muscles that are carrying excessive tension to begin with. This state of affairs is analogous to driving a car with the emergency break on. It limits our range of expression, creates wear and tear, drains our energy, and makes living and moving seem more difficult than it needs to. This tension usually exists below the level of conscious awareness, so that we do not even realize that we are carrying it, nor are we in touch with what it feels like to truly relax.
Where does this unconscious tension come from? From every negative emotion you have ever felt and not fully expressed. From every stress-inducing situation that did not come to a complete and speedy resolution. From every impulse you have ever had to control the way you appear to other people.
How can we release it? Through somatic therapy and emotional release modalities: somatic experiencing, yoga, hypnotherapy, biofeedback, acupuncture, massage, breathwork, meditation, qigong.
And, of course, tai chi.