Each year of life comes with changes, both good and bad, but some birthdays are more turbulent than others. From life crises to big changes, here are the years we are most likely to remember, and why.

Midlife And Quarter-Life Crises

A personal crisis is defined as a crucial or decisive point or situation, especially involving a difficult or unstable situation. These can happen at any time in your life, but for some reason, they are more common at the “quarter” and “halfway” points.

We may be more likely to make big life changes in birthdays ending with "9." Photo Courtesy of Pixabay

According to The Guardian, the “quarter-life crisis” is a relatively new concept; it's the result of having to cope with anxieties about jobs, unemployment, debt, and relationships in a broken economy. The quarter-life crisis is more likely to affect educated professionals and occurs between 25 and 30. The quarter-life crisis is characterized by four phases: feeling “locked” into a job or relationship, a growing sense that change is possible, a period of rebuilding a new life, and developing new commitments, interests, aspirations, and values.

"Plenty of people are going to say the quarterlife crisis doesn't exist," Damian Barr, author of the book "Get it Together: A Guide to Surviving Your Quarterlife Crisis," told The Guardian. "The truth is that our 20s are not, as they were for our parents, 10 years of tie-dye fun and quality 'me' time. Being twentysomething now is scary – fighting millions of other graduates for your first job, struggling to raise a mortgage deposit and finding time to juggle all your relationships.”

The midlife crisis, on the other hand, generally occurs in a person’s 40’s and early 50’s, and though similar to the quarter-life crisis, it is characterized by its own set of traits. It is characterized by feelings of dissatisfaction, whether this be with your marriage, career, or health, and involves making quick changes in an effort to remedy this dissatisfaction. This may involve making drastic decisions, such as divorce, buying expensive material things, and leaving your family.

Although the midlife and now quarter-life crises have become very much entwined with pop culture, many experts suggest they are a myth and that there is really no age that predisposes you for personal crises.

"There can be times when things crystallize as very problematic, a very deep disturbance in your life," Alexandra Freund, a life-span researcher at the University of Zurich in Switzerland told Live Science. "People experience these types of crises, but they are not at all related to age."

Having An Affair

Unfortunately, affairs are far more common than you may be comfortable believing, and one survey suggested that as many as 25 percent of married men had at least one extramarital affair, The Washington Post reported. However, research suggested that there may be certain ages where we are more likely to have an affair than others. According to one report, individuals are twice as likely to cheat in at the turn of a decade in ages that end in the number five, Live Science reported, although the researcher admitted that the findings weren’t exactly definitive.

However, not all “five years” may be created equal and other research suggested men and women are more likely to cheat when they are young, and although this correlation between youth and infidelity is significantly more pronounced in women, Big Think reported.

“Between about age 35 and age 50, people tend to be focused on careers and child-rearing,” Dr. Kelly Campbell, a psychologist and associate professor of psychology and human development at California State University, San Bernardino told The Wall Street Journal. “You have a greater chance of cheating when you’re younger or older.”

Make Big Life Changes

Individuals are most likely to make big drastic life changes at years ending in nine. It seems that the idea of entering a new decade changes the way people view their current life situation, and may spur them to make extreme changes — for better or worse.

For example, according to New York Magazine, runners tend to finish 2.3 percent faster when they race at 29 or 39 when compared to the years before that birthday. In addition, the same data showed that of 500 runners aged 25 to 64, a shocking 74 percent of them were in the last year of a decade. On the other hand, NY Magazine reported that the rate of suicide for people in the last year of a decade was slightly higher than the rate for any other age.