Rugby-O'Brien only looking forward after coming back from injury
The British and Irish Lions flanker starts in the back row for the second-ranked team in world rugby against Argentina in Dublin, having recovered from both shoulder and hip injuries.
His absence meant he missed Ireland's Grand Slam success in the Six Nations Championship and he was also sat on the sidelines while Leinster claimed a historic double in the European Champions Cup and the Pro-14.
O'Brien's previous injury setbacks have meant he sat out Ireland's historic win over world champions New Zealand in Chicago two years ago, as well as the 43-20 World Cup quarter-final defeat by Argentina at Cardiff in 2015.
"That's just the environment we're in. That's the life of a professional sportsman. You have to get on with it," O'Brien told reporters on the eve of his comeback international.
"I can't keep saying, 'Oh, I missed out on this, I missed out on that.' I have to look forward.
"Obviously, you have mixed emotions when there's stuff that happened. You're so happy for the lads, the effort they've put in, because you know what they've done to get there, how hard they've worked.
"Then to finally get to that place is brilliant for them.
"Obviously, you are disappointed as an individual that you have been injured and you do miss out on those big days. I have probably been more unlucky than others missing out on big days," he added.
Ireland are hoping his return will help their push towards success at next year's World Cup in Japan where they have legitimate ambitions of success, but O'Brien is only setting himself small targets as he works his way back.
"Obviously going through what I've done in the last year, I've assessed where I am and where I want to be. Starting from now and in the future. I've set myself little goals and I don't want to take a step back from that." the 31-year-old added.
"I want to keep building nicely. That's the stubborn part, where I won't give in to it. I want to get back to being one of the best players," he continued.
"I definitely think over the last year, I suppose, I realised how important it is to enjoy every opportunity you get in this environment and even the province.
"It's making the most of the time you have. That is the thing I've been telling myself, to make sure you go out and do your best every time. That makes it even more special." (Reporting by Mark Gleeson; Editing by John O'Brien)
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