Barca won the first leg of the quarter-final 1-0 on Wednesday, with Lionel Messi's 85th-minute strike separating the two sides.
Messi reacted quickly after his penalty was saved by Atletico goalkeeper Jan Oblak, tapping in the rebound and giving Barca the upper hand heading into next week's return clash in Madrid.
But Luis Enrique was not getting carried away and knows what a tough challenge progressing will be.
"It is a very positive result," he said afterwards.
"I am very content with the result, it is a fair result, and we are optimistic as we prepare for the return game.
"Knowing the rival, their coach, and knowing how they have behaved over recent seasons, I see it as 50-50 still.
"Despite what we have achieved today, our objective will be to go to the Calderon and win the game."
Croatian midfielder Ivan Rakitic echoed his coach's sentiments, and is aware Atletico will put significant pressure on his team next week.
"We must be prepared for the return leg," Rakitic told Barca TV.
"The 1-0 benefits us, but it's still all very open. They press much more at home. It'll be very difficult."
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