The Brazilian feels his side can take heart from its 3-0 win in Glasgow and is optimistic about his team's chances of reaching the last 16 of the Champions League.
The Rossoneri have started the campaign in poor form and currently sit 13th in Serie A, but claimed a vital Champions League win at Parkhead - their first on the road this term and their first triumph in eight games.
The Brazilian midfielder believes that he and his teammates can take heart from the result and use it to boost their domestic form.
"The victory is extremely important regardless of our previous results," the 31-year-old told reporters. "It is an essential victory and we achieved the result we wanted. For me, the biggest surprise was the result. I was not expecting it to be like this, but this shows the way we played. We worked hard to get a good result and in the end it was a fair score and we deserved it.
"We knew that if we won tonight we would have a decisive game against Ajax. This is what happened and now we depend on ourselves. We play at home, where we can get a good result. A victory or even a draw would be enough for us to qualify.
"This victory arrives at a good time and we needed a good result to improve our confidence. Every day I feel better, every game I feel better. I am happy with the way I'm playing and with the way things are going. I'm scoring lots of goals. I feel fine and I'm happy."
Kaka netted the first of Milan's goals with a header, with Cristian Zapata scoring the second before Mario Balotelli wrapped the match up.