Modric conceded he was struggling to match past standards he had set with the club.
Speaking with Slaven Bilic on Arena Sport, Modric admitted: "It wasn't easy, because I spent 13 years at the same club. One of the best periods of my life. I arrived relatively late, but at the right time, after four years in England. I was ready.
"Everything I experienced seems unreal to me. If someone had told me to write about what I wanted, what would satisfy me, I would have been afraid to write about what I later achieved. You know what kind of club Real Madrid is: it doesn't tolerate mediocrity, and maintaining that level for so many years is perhaps the most incredible thing.
"When I arrived, I would have thought it would be great to stay for five or six years; for a long time, I thought reaching 35 in football was extremely difficult, and I did it.”
Modric didn't hide the fact that going to Milan was a step down, but insists they're the closest thing to Real Madrid.
He explained: “Everything that comes after Real Madrid is a step backwards , there's no doubt about that and all the players confirm it, but I think I've arrived at a club close to Real Madrid in reputation and history.
"It's the most ideal situation that could have happened to me, especially because I love Milan like a child.”