Scotland manager Craig Levein has not picked Commons since the 2011 Nations Cup, and the former Hearts manager's continued stance has led Commons to focus his attentions on club football.
Commons said: "I think when I first came up to Celtic, I probably took it for granted that I would always be in the squad or playing. It felt like I was just part of the set-up.
"But now I haven't been involved for a long while, so it's just at the back of my mind.
"I think it's probably why I'm playing so well at the minute as I'm focusing all my efforts on Celtic."
The 29-year-old has scored 19 goals in 66 matches since joining Celtic in 2010.