He explained his raw emotion to NHL.com's Lou Korac on Wednesday.
"Because it's harder and harder every time," Perron said, according to Korac's In The Slot blog. "It's so hard on the mental side of it to go through. Basically, you have some situations that heal up quicker, and some that linger and there's no reason why, and that's why it gets harder on you, it gets harder on your family, you start to wonder about other things and you get in your head a lot.
"It's just good to be back. I think when you play, you think less and everything kind of settles."
Perron suffered his first concussion during the 2010-11 season after taking a blindside hit from Joe Thornton. He ended up missing 97 games.
Perron's since suffered multiple concussions. His latest head injury, which forced him to miss 24 games, caused him to think about the bigger picture.
"There's so many things that are hard mentally," he said. "You feel different as a person almost. ... I really, really hope - knock on wood - that it never happens again just because I don't know how many more times I can go through this."
He noted a wide variance in how long it takes him to recover from concussions.
"Last year I had one and I was out 10 days," Perron said.
The 30-year-old veteran is in his third stint with the Blues. He has 20 goals and 20 assists in 48 games this season, including five points in three contests since rejoining the lineup.