within reason

Now, Mrs. Clarke did tend to believe in the supernatural, within reason.

“I do realize that Mrs. Clarke was just now imitating a bullfighter, and therefore you must have thought it was a splendid idea and an enjoyable way to pass the time. And it is, certainly, but only within reason. Do you understand?”

“Within reason” is not the sort of place one can easily find on a map; in fact, its location may vary considerably from one day to the next.

Keep your curiosity within reason, and do not let your questions go overboard.

You are rich if you feel rich — if you can live a comfortable life and do the things you want to do, within reason.