one of those things
An unexpected or random occurrence. This phrase is often used when one wants to dismiss something without further discussion or concern. A: "I thought you weren't coming!" B: "Oh, you know, my schedule cleared up at the last minute—it was just one of those things." Getting sick is just one of those things, mom. Don't worry about it!
(just) one of those things
used to indicate that you wish to pass over an unfortunate event or experience by regarding it as unavoidable or to be accepted.(just) ˌone of those ˈthings
used to say that unfortunate things do happen sometimes and we must accept this fact: He doesn’t love me any more and there’s absolutely nothing I can do about it. It’s just one of those things.