The former British Open champion and 2001 Masters finalist decided to move into other aspects of the game, including media work and coaching.
O'Brien was demoted from the Pro Tour last year, but quickly regained his status as a Q-schooler.
However, he opted out of the world
snooker (loanword)
The tourney, at least on the table.
In an interview with RTÉ Sports, he said, "I was initially saddened by the idea of not playing anymore because obviously I've been a professional for 33 years. It's been my life.
"I can play on my own and, you know, be happy as much as anything, just playing. So obviously I'll still play, but obviously not the same amount or intensity. I'm going to miss that.
"I've always enjoyed practicing, too. It's never been a difficult or a feeling of making sacrifices for it. I've always enjoyed it, but obviously, going back to the day I started playing here at 10 a.m. for five or six hours.
"This may also be another small challenge. The routines won't be as set up. Going to bed early at club practice.
"Obviously, I had some success. Of course, I would have liked more, but I think ultimately for me, you know, not to sound too cliché, the journey is the reward. I always wanted to play snooker.
"I love playing snooker, even the bad days and disappointments are still satisfying in some ways. You're still alive. You still feel something.
"I like to play ball. I wouldn't want to do anything else. But as I said, I'm lucky now that I have other options in snooker. That will soften the blow.
O'Brien already spends time mentoring young players and wants to expand that work.
"In years past, there was a Plan B," he added.
"Obviously I've been busy coaching for the last year or two and fortunately this season I've started to do some commentary for Eurosport.
"Outside of the game, the two best things for me are making comments and then coaching. It doesn't get that bad.
Aaron Hill has been waving the flag for the Republic of Ireland this year with some excellent performances, including a quarter-final at the Wuhan Open.
O'Brien has also been impressed with two other Cork players and has already worked with Hill, hinting that he may try to help the next generation of Irish players.
He added: "Aaron has potential and a great game. We're starting to see him establish himself on the tour. Once again, he's going through this learning process, almost like an apprenticeship service. He fell off the tour and started over through Q-school. As you can see, this may have toughened him up again.
"He's struggling. He's hungry. That's the main ingredient. There are a lot of talented players around the world. But how bad do you want it to be and what are you prepared to do about it? He seems to tick those boxes pretty well.
"As well as Aaron Hill on tour, there are two young lads from Cork, Ross Bulman and Leon Crowley, who are on the rise.
"They certainly have a lot of potential to play on tour and certainly achieve in tournaments.
"Maybe for someone like me who has a great amateur structure, it's a way to work with lads who want to go pro.
"They don't have to make a lot of mistakes because I've made them.
"I have 30 years of experience (which may be useful for players just starting out now).
"Playing snooker is easy. It's the journey, it's the preparation, it's dealing with disappointment, your expectations, other people's expectations, and a million and one other things that obviously I went through.
"I definitely think there's some role to be played there in trying to push it (to be a mentor for Ireland).
O'Brien is also targeting roles that could bring the tournament back to the Republic of Ireland.
The Northern Ireland Open in Belfast is an annual tournament, but he is keen to bring another event to the southern islands.
He explained, "When I stopped playing it was probably another project for me and I think you can definitely get a ranking tournament somehow, even an Irish Masters or something like that, which we had at the time, which was fantastic.
"Obviously Goffs is still there and it's still a great venue. It's used for some of the senior races and I think maybe if you had RTÉ, Goffs and then a big sponsor, I think you could still run it.
"The game is still popular here and I think there's a market there and if you have a well-run tournament you're going to get people to play.
"So hopefully in the near future, young players like Aaron Hill will be able to play in their countries and further promote the sport.
