Jung's typological model regards psychological type as similar to left or right handedness: individuals are either born with, or develop, certain preferred ways of thinking and acting. The MBTI sorts some of these psychological differences into four opposite pairs, or dichotomies, with a resulting 16 possible psychological types. None of these types are better or worse; however, Briggs and Myers theorized that individuals naturally prefer one overall combination of type differences. In the same way that writing with the left hand is hard work for a right-hander, so people tend to find using their opposite psychological preferences more difficult, even if they can become more proficient (and therefore behaviorally flexible) with practice and development.
Comment: I find acting as my opposite type so difficult that it amounts to psychological torture.