City came from behind on Saturday to win the fourth round tie 2-1.
On manager Pep Guardiola, Lewis insisted: "He wasn't going mad or anything like that. He knew we'd created chances and it's about keeping going in an environment like this.
"Credit to Leyton Orient, they made it difficult for us to play. It's easy to say it's tougher than you think but we all know they're tough. The crowd are right up for it.
"It's Man City at the end of the day, the demands are so high. There's enough leadership in this team. Going from attack to defence is difficult, there's a lot of ground to cover. It's all about trust.
"The season hasn't panned out how we wanted it to. Every game now, as long as we win, it could be a great season for us.
"Everyone does want us to get beat, apart from City fans of course. it's pressure on our shoulders. Everyone settled their heads at half-time."
On facing Real Madrid in their Champions League playoff this week, Lewis added: "It's a huge game, the name itself tells you the story. It's a game you see every year at the moment, whether that's in the quarter-finals or the semi-finals."