This article originally appeared in Psychology Today.

Have you ever thought, “I should be happy and excited! I’m making a good change in my life – so why am I so stressed?”

You’re probably stressed because almost any change, whether it's positive or negative, whether you wanted it or it was a surprise, can create stress. In fact, since 1967, when psychiatrists Thomas Holmes and Richard Rahe published findings from studying the medical records of over 5,000 medical patients, therapists have known that both unhappy and happy life transitions can even lead to emotional and physical distress. Highest on the Holmes and Rahe list of stressors are painful life changes, including the death of a spouse or close family member, divorce, marital separation, imprisonment, and personal injury or illness.

But positive changes rank close behind. Marriage, marital reconciliation, pregnancy, childbirth, job change, retirement, and moving homes, all often positive experiences, also range high on the list of life stressors. Although some people embrace and even seek out change, most of us resist it, even when it’s about something we really want. Learning to manage transitions may be one of the most important lessons of your life.