The Dane was sent off when he brought down Cristian Brocchi to give away a spot kick in their 2-1 defeat to Lazio.
“The referee could give the foul, I guess. It wasn’t a huge foul, but I did stretch out my arm and Brocchi was clever, as he turned to the right as soon as he felt contact on his left arm,” Kjaer told Sky Sport Italia.
“Seeing that, the official awarded the penalty and flashed the red card that effectively ended the game.
“It was a bad time for me and two really tough days. Fortunately, my family helped me get through it.
“I was above all upset for the fans who cared so much about this very important game, but now I feel better. We have to look ahead to beating Palermo.
“After that I am already focusing on the next derby and winning that one for all the Roma fans.
“So many people came to reassure me over the last couple of days. They said I have to look forward and not think about it anymore. They let me realise it is only a game, albeit a very important one for all the supporters.”