How important is it to feel comfortable during sexual intercourse?

It is essential to feel comfortable before, during and after a sexual intercourse. Whether it is the first sexual experience or the thousandth, it is always important to feel safe enough to change your mind and to not proceed if desired. This is because agreeing to engage in sexual activity with someone does not mean that you cannot change your mind for various reasons ranging from changes in mood to a lack of desire that was once there, or because there are things you have learned that you do not like, or even because of an argument beforehand, etc.; feeling comfortable is a right that must be respected and maintained in a relationship between one or more partners, for all the individuals involved.