The Criteria of Emotional Maturity
by William C. Menninger, M.D.
The ability to deal constructively with reality
The capacity to adapt to change
A relative freedom from symptoms that are produced by tensions and anxieties
The capacity to find satisfaction in giving than receiving
The capacity to relate to other people in a consistent manner with mutual satisfaction and helpfulness
The capacity to sublimate, to direct one's instinctive hostile energy into creative and constructive outlets
The capacity to love
There you go. Seems like the last criterion is the simplest one and I thought, "Hey, I could do that!" But eventually I came to realize it is in fact the most difficult thing to do. Because love is encompassing and this love does not only pertain to romantic love, which is most likely our instinctive reaction after reading the last criterion.