Two people in a relationship often began their association by flirting with one another. Over time, they become involved in their lives, and they forget the simple joy of this type of interaction. Flirting is a healthy way to lighten a relationship, and it can re-ignite lost feelings of fun for a couple. When they take a few minutes to flirt with each other, they will begin to remember what originally attracted them to each other. This is a good behavior to make into a regular habit.
When someone is involved in a relationship, the choice to flirt with people outside of that relationship has to take their partner's feelings into account. A person who is not jealous will have no objections when their partner flirts, but it can cause issues if it happens too often. A natural flirt sees nothing wrong with their behavior, but their partner must have enough trust in the relationship to know it will go no further.