As children we don't have the resources to deal with tragic events and trauma, emotional pain is overwhelming so the body shuts it off. The body comes to the defence of the whole being, doing things to stop the pain from being fully experienced. But long after the event has passed, the body continues its defence of the whole-self, causing problems in the body that will persist into adult hood until the issue is released.
Stress triggers your sympathetic nervous system - flight or fight stimulating the release of cortisol and adrenalin which suppresses the immune system, increases blood sugar and decreases bone formation. Yoga stimulates the release of good hormones, oxytocin and prolactin from the pituitary gland are responsible for feelings of love and it stimulates the vagus nerve which slows the heart rate and blood pressure, allowing you to relax and gives you a sense of well being.
By gently working on sore parts of the body through yoga we can gently persuade tight muscles to loosen and in the process free old frustrations and emotions.
I know yoga usually makes you feel wonderful but occasionally it happens that you find tears rolling down your cheeks, maybe you can identify the cause of the emotional flood or maybe you can't. What has happened is a posture has opened up an old repressed emotion and let it out, the tears are a cleanse and more than likely afterwards you are going to feel like a weight has been lifted and you can see your way forward into a bright new freshness. There may be more work to be done, but you have made an amazing break-through allowing things to change and you open up to new opportunities.
Yoga is partly about recognizing and accepting that things change, it frees us from attachment to things that have passed their use-by date. As the earth spins through space we see the sun move across the sky; the constellations appear and disappear; the seasons come and go; the tides ebb and flow with the phases of the moon; flowers bloom and wither. As we practice yoga we watch ourselves change as we transition from posture to posture, watching changes in our breath, heart rate, body temperature, blood pressure, muscles relaxing. You can even watch your emotions change through the practice. Our feelings and our thoughts are also constantly changing. Resistance to change or holding onto the past causes the body to tense and tighten up blocking the natural flow of energies through the body, the energy can get stuck creating blocks in the form of a tight hip, sore back or frozen shoulder or a myriad of other pains. Physical and emotional pain is a signal to the brain that there is something wrong and needs to be worked through both physically and mentally.
If we try to block out an emotional pain because it hurts too much, we are denying ourselves the chance to grow and the pain will persist affecting your body. An emotion is what you feel, it may be a part of you, but it doesn't define who you are. Just because you feel sad doesn't mean you are a sad person, the same with other negative emotions like jealousy, anger and frustration, it's normal to feel them but don't become them. Many people can't see through a negative emotion, they let it take them over, it becomes who they think they are and they often take the negativity out on others which only serves to make themselves feel guilty, perpetuating the negativity.
With practice it is possible to observe the negative emotion, to accept that it is a part of you at the time, the emotion will soon pass. If you give it space to be what it is without interfering with it, it will go away. In this way you open yourself to fully experience the emotion and have the knowledge that it will change because that is the nature of emotions - they change. This is also the case with positive emotions, it is just as important not to be attached to positive emotions if you wish to obtain equilibrium, give them space and feel them fully, they will change. But as we free negativity there is a whole lot more space and time to fill with positivity. If you try to push a negative emotion away it will persist, niggling away at you. By believing in an emotion we give it substance and power over us, by believing in the story of why it should be there we are giving it fuel. Instead of trying not to feel it or over analyzing and getting involved in the story, allow yourself to feel the raw emotion, when you look at it fully it looses it's grip, it looses its power and it changes or dissolves. You liberate it and you liberate yourself.
I know for myself it is a bit of a roller coaster as extremely good and extremely bad things seem to happen in my life. I keep observing and let myself feel, I don't get scared of what I'm feeling, even when it's kind of scary because I know that it is going to change when it is ready. I just keep on being myself and tell myself that everything is going to be ok.
Negative emotions can arise out of nowhere during yoga practice. When unsuppressed, these moments are giving you a chance to liberate them and offering you a chance of renewal. Every moment is a new moment, a chance to start afresh with renewed fresh energy so let go of the old energy and allow yourself to be filled with new vitality.