"I know people that are depressed and he was not a depressed person. This was not planned. He would be mad if he knew he died, he would be so p***ed off," Pasternak told pagesix.com.
Miller, who died last week from an apparent overdose at age 26, started training with Pasternak -- a Los Angeles-based trainer-to-the-stars -- a year and a half ago.
Pasternak also revealed that he was expecting Miller to walk into his studio on the day he died.
"I was mid-session with someone else expecting him to show up about 45 min later. One of the ladies who works with me walked in with kind of a blank look on her face and held up her phone and there was a news release (about Miller's death)," he said.
Remembering the good days spent with Miller and Grande, Pasternak said: "Ariana was such an incredibly positive influence on him as she's someone who kind of lives a very healthy lifestyle.
"He thought that Mac and I would be a good fit for each other and he got hooked (on working out), it took him a bit but when he got into it, he loved it."
He further said that Miller was always in high spirits and was most looking forward to going on tour following his album release in August.
(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)