Last Saturday's 2-2 draw against Samp meant Cagliari remain with just one win after four Serie A matches ahead of Wednesday's game at Livorno.
Lopez is frustrated that the Sardinian outfit lacked the discipline to seal the victory having gone in front two minutes from time.
However, Cagliari failed to clear a ball in the area in what was the last play of the game and Sampdoria's Manolo Gabbiadini made them pay.
"We were naive," Lopez said. "You cannot give away a goal in the last seconds of the game.
"I guess this is football and we have to accept it.
"But this will be a lesson for my players.
"They will learn from the mistakes because that is the way you mature.
"Now we must look ahead to our game at Livorno and try to get back on track.
"I know this team is capable of easily defending its Serie A status, which is our main aim this season."
Like Catania, Livorno's main aim this season is to avoid the drop.
The Amaranto are showing few signs of weakness since returning to the top flight this summer.
Despite losing their league opener to Roma 2-0, Livorno bounced back with wins at Sassuolo and against Catania before holding Genoa to a goalless draw in Liguria.
"It is never easy to play in Genoa so I'm happy with the point," Livorno coach Davide Nicola said. "I believe it was an important test for my players and we played a great game.
"We made life difficult for Genoa and we had the best chances to score.
"We now have to continue on this path."
The hosts will be without pivotal midfielder Marco Biagianti, who sustained an ankle injury at the weekend.