City go to Real needing to overturn a 3-2 aggregate deficit to reach the Champions League round of 16.
"You have to make an almost perfect game, obviously,” Guardiola said.
“The result is not the perfect situation. We have to attack and score goals, this is the idea.
“We will have to play an almost perfect game to go through.
“It’s the same going to Arsenal or Liverpool right now or Barcelona, the big teams qualified for the top eight, it is quite similar.
“It will be tough going away. Especially after the result we took in the first game.
"Play with courage. Be yourself. I learned that as a young player when we didn’t get results.
“Play with incredible courage and play to win the game, otherwise always you can lose but you must be yourself.
“When we did well here it is because we played to win the game. We have no alternative because of the result in the first leg.”