Watford will host United on Saturday with boss Ranieri insistent the Hornets can quickly climb the Premier League table through hard graft.
But the 70-year-old Italian boss thinks his players must love the intensity, just as he admits relishing the pressure of top-level management.
“Look, managers are always under pressure, in every country, every moment – also 20, 30 years ago,” said Ranieri.
“That’s our life; we are alone, we have to fight, we have to be very clear with our players, and try to do our best.
“Well, the pressure, my life is pressure, is under pressure every time.
“I love this kind of pressure. I think I do this job for the pressure.
“I’m alive when this kind of duel between a big team and an underdog team (happens).
“I want my players to show their character, arrogance and to do their best.”
Battling Watford pulled off a stunning 5-2 victory at Everton on October 23 to give Ranieri lift-off in his Vicarage Road challenge.
Consecutive 1-0 defeats to Southampton and Arsenal stymied that progress before the international break, but now the ex-Chelsea and Leicester boss believes the Hertfordshire side can kick on back to form.
United have endured their own struggles, with beleaguered boss Ole Gunnar Solskjaer only able to inspire the Red Devils to two wins in their last seven matches in all competitions.
Ranieri believes Solskjaer can soak up that criticism, however, as the Old Trafford club continue to seek a route back to the Sir Alex Ferguson glory years.
“But look, Solskjaer is doing very well; of course, Manchester United want to win every time,” said Ranieri.
“And they want to come back to the Alex Ferguson era, that’s normal.
“But the pressure is a positive pressure, for him and for everyone working in Manchester.”
Watford will come up against Cristiano Ronaldo in his second Manchester United stint.
Ronaldo has already starred on his United return, though the 36-year-old’s presence has create several wider tactical headaches for Solskjaer.
Ranieri insisted, though, that no manager would turn down Ronaldo’s services, joking that he would welcome the Portugal forward with open arms.
Asked if having Ronaldo in a squad would cause any concerns, Ranieri replied: “Oh no, no, no: give me Cristiano, please! It’s no problem for me, I’d leave him to play all the minutes!
“Cristiano is one of the best players in the world, and he’s good for football, because I think a lot of young boys are looking at him and the best players in the world and it’s a good attraction for football.”