Every man has his hobby-horse.

The saying observes that everyone has some favorite interest, subject, or pursuit to which they return with unusual enthusiasm. A person's hobby-horse may be a harmless enjoyment, but it can also be a topic they repeatedly raise.

It can gently excuse another person's recurring preoccupation by treating it as a common human tendency. Depending on tone, it may also criticize someone for pressing a pet concern too often or letting it dominate conversation.

Use it for a person's characteristic pet interest or recurring theme, especially after they return to it again. It suits lightly humorous or mildly teasing remarks, though a sharper delivery can sound dismissive. Its generic use of “man” may sound dated or exclusionary where inclusive language is preferred.