Neil Lennon can understand some Celtic fans' frustration and hurt following the departure of Kieran Tierney.
But he stressed top players move on and Tierney is no different even if he is a huge Celtic supporter himself.
Some supporters have expressed their pain and anger on social media after the 22-year-old chose to move to Arsenal for a Scottish-record €27 million fee.
"I can understand their point of view because they are Celtic fans and the only thing they see is Celtic," Lennon said.
"With Kieran being such a fervent supporter of the club, they might find it difficult to comprehend why he would want to leave Celtic.
"But as he has alluded to himself, he has had a great time here and probably achieved everything he wanted to achieve, and he is accepting a new challenge - a professional challenge as well as a personal challenge in his life.
"It's understandable it is going to hurt us because we are losing a very good player but these things crop up every now and then in football.
"All teams sell good players eventually and Kieran is no different in that regard.
"His ambition was to go once Arsenal really showed their interest. Obviously it was protracted because we couldn't agree a deal.
"You are trying to keep him calm and here mentally but on the other side it was an opportunity he was probably thinking about almost on a daily basis."
Celtic rebuffed interest in Callum McGregor after Lennon's predecessor, Brendan Rodgers, launched a late attempt to take the midfielder to Leicester.
"We are not interested in selling any of our better players now," Lennon said.
"It's well documented that there was interest in Callum. It was just an approach, no bid. That's over now and we will settle him down.
"He is playing as well as he has ever done and hopefully he will again have another fantastic season as he has done the last couple."
While some fans are struggling to come to terms with the fact that Tierney's personal ambition could outweigh his loyalty to Celtic, Lennon believes the record fee and interest in McGregor is a positive for the club.
"I think it's a fantastic example of the work that's done behind the scenes, not just at academy level but development coaches, first-team coaches and the way the club is hell-bent on developing their own," he said.
"We take a huge amount of pride in home-grown players coming through.
"Kieran is the latest one and obviously Jamesy (Forrest) and Callum and now Mikey Johnston are making significant contributions to the first team.
"And that shows the younger ones that there's a pathway here if they do the right things and protect their talent. If we recognise the talent there is a real ambition and opportunity to play first-team football on a regular basis.
"We have some good ones bubbling under. Look, it's not a conveyor belt where you can produce, one, two, three a year.
"It's very, very difficult to produce a quality long-term first-team player but we have done that over the last 10-15 years very well compared to a lot of other clubs."
Another player who attracted interest was Scott Sinclair but no move materialised for the winger despite being linked with the likes of Preston and Derby.
"He is finding it difficult to get in the squad at the minute but it's very early days and once the season goes on you will imagine Scott will make a contribution," said Lennon, whose side travel to Motherwell on Saturday.
"There was interest in him, that never materialised fully and he is in the squad for Saturday."