Second Wind 1978

Directed by Gérard Blain

An aging dentist looks for a little liveliness by abandoning his wife in favor of a younger woman. When he learns that his mistress also has another younger lover, he gets jealous, but tries not to make an issue of it. In the end, he dumps her and returns to his wife, who is not about to stand for his middle-aged immaturity. She leaves him.