Jack Osbourne 's tearfully remembering a moment he and his late father, Ozzy Osbourne , shared a couple of weeks before his death ... and he says, in hindsight, it couldn't have been more perfect.

Ozzy's youngest child got emotional Monday on 'GMA,' when he opened up about the pain of losing a parent. He also talked about how his mom, Sharon , is handling life without Ozzy ... saying, she's "okay, but she's not okay." Getty

Jack started choking up when he talked about Ozzy being clean, sober and in "such a good mood" at the end of his life ... even though the late rocker once said, "If I were clean and sober, I wouldn't be Ozzy."

During Ozzy's final performance -- the July 5 tribute concert -- Jack reveals he took a moment backstage to run back to the dressing room, and

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