Midlife crisis is a term used by people in their late 40s and early 50s where one faces an existential crisis while others lose their sense of satisfaction in life. One key reason is the changes that have happened in their life like body and health as well as relationships. However, a Midlife crisis is a good signal of call-to-action to find a new meaning in life, such as finding a new hobby, to find a new purpose, or to learn something new.
Source: https://www.lifehack.org/884916/what-is-a-midlife-crisis