It's a way of showing your approval of another person, a kind of congratulations. In ancient times a person might place a hand on another person's head or shoulder to say the same thing. It probably made you feel better for two reasons. First, the medicine soaked into your skin and may have produced heat to comfort you. Second, you were helped by the physical touch of someone who cared.
Chrism does the same thing.
God is touching you and offering to heal you of whatever stress you feel from growing up. We all need this physical contact with others we love. Some doctors put on rubber gloves whenever they touch a patient. They may fear AIDS or other diseases. God never does that.