This article is written by Ashley Lauretta on Elle.com

A few years ago, my best friend of over a decade called me and I chose not to answer. We were living in different states and hadn’t seen each other in months; in his voicemail, he was crying. How had I not known something was wrong? When I called back, he didn’t answer. My husband—at the time my boyfriend—watched as I cried for an hour because I wasn’t there for my friend like he had always been there for me.

This wasn’t an isolated incident: It was one of many unanswered calls, one of many commitments left unfulfilled. I wasn’t always this way. In high school, I never missed an episode ofOne Tree Hill, but almost every other night was spent with friends. I wasn’t exhausted after an hour of conversation. I didn’t excitedly make plans only to say, “I don’t want to go,” 10 minutes before said plans were to take place. Now, all that has changed; even though I’m lonely, I can’t stop isolating myself.

I work from home as a freelance writer and that leads to at least eight hours each weekday I am guaranteed time by myself. Why do I still crave alone time after my husband gets home, preferring to curl up with a television show? Why can’t I just convince myself I will have a good time at an event and go? Why is my first instinct when a friend tries to make plans to say no?

While introversion is a concept that gets thrown around loosely, it’s not synonymous with shyness. “In most psychology circles, the term introvert, popularized by Carl Jung, is used to describe a person whose focus of attention is primarily on his or her own thoughts and feelings,” explains Dr. Simon Rego, director of psychology training at the Montefiore Medical Center/Albert Einstein College of Medicine in New York. Jung, the pioneering Swiss psychiatrist, used the concepts of extroversion and introversion to explain different psychological types.

However, today, many people are familiar with these concepts not from Jung’s work, but because of their use in the Myers-Briggs Type Indicator personality test, which, despitecriticism from psychologists, has been used in recent decades for everything from leadership training to marriage counseling. In this test, you answer a series of questions related to Jung’s idea of four cognitive functions—thinking, feeling, sensation, and intuition—that are related either to extroversion or introversion. My Myers-Briggs personality type is an INFJ—introverted, intuitive, feeling, judging—and out of the 16 possible combinations, Myers-Briggs notes this is the rarest, representing about 1 percent of the population.

I have always wished I could wear a sign that says, “It’s not you; it’s me. I’m an INFJ,” so that when I don’t smile or talk a lot at social gatherings people don’t automatically assume something is wrong. As an INFJ, I care deeply about others’ feelings, and in social situations, this leads me to spend a lot of time worrying about what others are thinking or feeling toward me. This can be especially true in times of conflict, as INFJs avoid disagreements at all costs for fear of hurting others’ feelings and because they are sensitive to criticism.

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