The Brazilian is unhappy at how far United are from the title contenders and other top sides.
Speaking after a 2-2 draw with Liverpool, he stated to ESPN Brazil: "It's difficult. This is the point that bothers me most about not fighting for titles.
"Being 20 points behind first place. Sometimes, I can't even sleep to try to think about doing something different. It's reality. There's no point in thinking about title or Champions League places, we need to think about today's games.
"We need to think about the day-to-day, we had the opportunity to score nine points in the last few games and we scored two. We were upset. We have to think game by game and focus on the next match, against Bournemouth."
On the game against Liverpool, he added: "The game was very fast-paced and well played. A classic. We were playing against one of the leaders of the competition and who is going through a good moment. We responded well.
"Both teams had opportunities. The game was good. At home we are strong, but we played against a great team. We have to think about the next match."