The Blues have a mountain to climb at Stamford Bridge as they look to overturn a 3-1 deficit from the first leg at the Parc des Princes last week.
Mourinho admitted that is was an "almost impossible" task, but believes that yesterday's victory over Stoke City, which ended a run of back-to-back defeats, will give his side confidence going into the match.
"A third defeat would be very bad for our confidence in relation to Tuesday's match. It was important to win, to have again a smile on the players' faces and to get more confidence," Mourinho is quoted as saying by PA.
"Now we can approach the match against Paris with a smile. It's what we need for such a difficult match and such an almost impossible job to do. I think the best way to try to do it is to have a smile and go at them.
"I want to enjoy that game. I enjoy the difficulty. Now we know that we need to win 2-0, 3-1, 4-1, 5-2. We know that we need a crazy result against Paris. We must be ready to go without fear, go at them and no problems and see what happens. If we have to lose to lose after a magnificent night of football, a magnificent night of emotion, if we have to lose."
Chelsea are aiming to reach the last four of the Champions League for the seventh time in the last 11 seasons.