Some verbs change their meaning entirely when they become reflexive. This is where Spanish gets expressive! (To go) vs. Irse (To leave/go away) Dormir (To sleep) vs. Dormirse (To fall asleep)
Also, not every verb that uses se is reflexive. Some are (always used with se , like arrepentirse – to regret) but follow the same conjugation rules. verbos reflexivos español