Rob Gronkowski gets emotional and explains why he had to step away from the game of football after nine seasons. (1:25)

Former New England Patriots tight end Rob Gronkowski became emotional Tuesday morning when describing his decision to retire from the NFL in March.

"I want to be clear to my fans. I needed to recover. I was not in a good place. Football was bringing me down, and I didn't like it. I was losing that joy in life," Gronkowski said, fighting back tears.

Gronkowski's remarks came at an announcement that he will be an advocate for players to be allowed to use CBD products for pain relief. He left the door open to possibly un-retire, saying, "physically, I could play right now" but added he is not there mentally.

Gronkowski detailed how he sustained a quad injury in Super Bowl LIII, and he knew that he was retiring after that.

"I got done with the game and I could barely walk," he said. "I slept five minutes that night. I couldn't even think. I was in tears in my bed after a Super Bowl victory. It didn't make that much sense to me. And then, for four weeks, I couldn't even sleep for more than 20 minutes a night. I was like, 'Damn, this sucks.' It didn't feel good.

"It was one of the biggest, deepest thigh bruises I've ever gotten," he added, noting it led to significant internal bleeding.

Gronkowski was 29 when he retired, the same age as Indianapolis Colts quarterback Andrew Luck, who shocked the NFL on Saturday by retiring because of the toll injuries have taken on his body. Gronkowski said he felt empathy for Luck.

Gronkowski told those in attendance in New York that he's in a better place now and "very satisfied with where I am in life now."

"I truly believe going through those tough times, nine years -- off the field, on the field -- has brought me to this point and I believe I'm on the right path in my life," he said.

"It's a purpose to have passion in my life, to have joy in my life. And then to inspire optimal health within myself, I need to do that in order to get to a peak and then I can bring it to other people. Because I know [in] the NFL, players are dealing with that kind of stuff, they're dealing with pain. I was. And I needed to walk away because I needed to do what was best for myself."