Mourinho meets his former club on Sunday in a crucial game for their top four hopes.
"I can't go worried into a game. It is not the ideal state of mind and it will not happen," he said.
"Neither with me nor with the players. We have to maintain confidence and enjoy, in a positive spirit, withstanding the pressure. Of course, we also have to be capable of having sufficient responsibility in such a difficult game and with this dimension."
Mourinho also remarked: "We are preparing well for the wrong reasons. We had a week to work when we previously had less time to work, but for the right reasons, which was, for example, being in the Europa League."