However, the Catalan stands by the decision to allow the City great to come off contract this season.
“Yeah, by far,” said the Manchester City boss. “I lived a lot of things with players like him. We have lived a lot of things with them, a lot.
"Good moments, in terrible bad moments. Without them, Sergio (Aguero), Kevin, David Silva, all the players, I could make a long, long list from my nine years here, there are a lot of players that come in and they leave.
“They are part of my life. We have lived here. It’s impossible you don’t feel it. Of course, it’s so difficult. Of course it is.”
De Bruyne has admitted in recent days at his surprise that City made no effort to secure him to a new deal.
Guardiola also said: “The feelings he has, and all the players have, I understand it completely. I understand. It cannot be otherwise. I wish personally for him and his family, on behalf of all the club, all the best.
"He behaves unbelievably all these years, and this month again, and it will happen until the end. He has trained really good.
“He is playing, helping us with his skills and his talents and I know he wants the best for the club. This is all we are concerned about, preparing for Nottingham Forest and not thinking much further than that.”