The reality principle is the exact opposite of the pleasure principle (which seeks immediate gratification). One is looked upon as more mature when they are acting in accordance with reality. As children we seek pleasure and try to avoid things that cause us suffering or pain, however as we get older we realize that there are certain situations where it is better to endure the suffering/pain than to be out of control or inappropriate. The reality principle is governed by the ego, which controls the instant-gratification mentality of the id.