What is surrender? Surrender is to no longer offer resistance to your present experience, to allow the external world, all thoughts and sensations in the body to be as they are, without interpreting them.
Without resistance and mental interpretation, the ego can not survive. All of the old harmful energies that still live in the body are burned up.
Surrender allows you to no longer be dependent on other people, situations or content of your mind to be a certain way before you can be at ease. Surrender takes the heaviness out of the form, and allows you to become aware of your own formless dimension. As a result the form is no longer such a disturbance, and your conditioning is replaced by intuitive and spontaneous intelligence.