The individual is able to, on an either regular or semi-regular basis, enter into voluntarily agreed and consensual situations involving partnered sexual activity, i.e. an activity other than solo masturbation. This would inherently mean there is at least one other person per situation, with or without sexual activity, and regardless of whether or not these situations are sexually monogamous; i.e., a “sex life” can be had just as easily with a long-term sexual partner as it can with multiple partners in rapid succession over a lifetime.
The idea of a ‘regularly or semi-regularly’ sex life varies, but categorizing an individual who is involuntarily celibate (as opposed to voluntary abstinence) as having a sex life may be inaccurate.
Presuming the above is true by default, the individual who has a sex life is then able to explore and deepen his or her existing sexual skills and also, when s/he desires it, is able to have the opportunity to learn new ones and to “grow” as a sexual being.
The individual is able, because of these factors, to have an “area” of his or her overall “life” that involves sex in a way that is somewhat similar to how athletes have an “area” of their lives that involves sports or how musicians have an “area” of their lives that involves music. A person with a secure and constantly developing sex life is inherently able to regard their sexuality as an active part of themselves, and although a secure sex life does not necessarily mean that the person will always feel self-confident or sexually attractive, consistent access to sex and the ability to deepen and broaden one’s sexual skills provides a certain psychological assurance of sex appeal that people who do not have a “sex life” tend not to have.