The Italians lost 3-1 to Barcelona in their Champions League tie on Wednesday night and are without a victory in their past five games, but Muntari is confident they can return to winning ways.
"We didn't want to lose against Barcelona, but at the moment things aren't going our way," he told Milan Channel.
"We want to do well and will soon emerge from this difficult time. Yesterday we played the way the Coach wanted us to and how we had prepared this match in training.
"Refereeing errors are also part of football, but we must work and keep our feet on the ground to overcome this negative period."
AC Milan visit AC Chievo Verona in Serie A on Sunday.