it's just one of those things
It is an unexpected or random occurrence, especially a negative one, that one cannot predict or prevent. A: "I was so sorry to hear about your father's sudden passing." B: "Thank you. We're still in shock, but it's just one of those things." My mom broke her ankle a month before my wedding in Portugal. It was really unfortunate, but it's just one of those things.
It's just one of those things.
It is something that couldn't have been prevented.; It is an unfortunate thing caused by fate. I'm sorry, too. It's not your fault. It's just one of those things. I feel terrible that I didn't pass the bar exam. I guess it was just one of those things.