Scott Brown admits the biggest concern over his international retirement was letting down Scotland boss Gordon Strachan.
Brown announced his decision last week in a bid to prolong his club career after suffering a series of injuries in recent seasons.
The 31-year-old did not want to leave Strachan in the lurch ahead of the World Cup qualifying campaign, but the Scotland boss understood his wishes and made no attempt to dissuade him.
Speaking in Israel ahead of Celtic's Champions League qualifier against Hapoel Be'er Sheva, Brown said: "My body has taken a lot over the years. I have played international football for 11 years, not any break at all really, season after season.
"The time has come for me. It's a sad day, I really enjoyed playing for Scotland all along.
"I think the biggest thing for me was to think about letting the gaffer down. He brought me to Celtic at the time and he means so much to me.
"We spoke and it was wonderful to be honest."
Strachan said his Scotland squad remains strong in central midfield following Brown's retirement.
Strachan could call upon Darren Fletcher, James Morrison, James McArthur, John McGinn, Kevin McDonald and Barry Bannan after naming his squad for Scotland's opening World Cup qualifier in Malta on Sept. 4.
"Listen, I'm OK there," Strachan said. "It's one of our stronger areas. Weaker without him, but still strong.
"It will be quieter. I loved his company, I think everybody liked his company. But we get on with it. We thank him for what he did. We understand the decision he has come to, as a player myself, who had 50 caps, and we respect his decision.
"His decision is for the best of Scott Brown. At times in your career you go: 'What's the best for me? What's the best for my family?'
"And he has decided at this moment in time that this will be the best for him."
After enjoying a proper summer break for the first time in years, Brown insists he will not return to the international fold.
He said: "I need to look after my body and try to play at this club as long as I can. "I have had a great preseason, I had five weeks off in the summer and my body is feeling good.
"It has probably been five or six years since I had a break like that. My legs are feeling fresh and hopefully now I can push on.
"Once my mind is set that's it. For me there's no going back. I am quite stubborn that way. It is good timing for everyone I think.
"I have not seen family, or chill-out time so I think it is a good time for me to call it a day. I just want to push and prolong my Celtic career as much as I can."