Madrid proved too strong for 10-man Levante at Santiago Bernabeu as efforts from Cristiano Ronaldo, Marcelo and a Nikos Karabelas own goal settled the match in the hosts' favor.
David Navarro saw red for the visitors as Los Blancos seized on the opportunity handed to them by Barcelona's defeat to Real Valladolid on Saturday.
However, Ancelotti is taking nothing for granted, despite seeing his side extend its unbeaten run to 29 matches in all competitions.
"We have to start focusing on our next match and try to win it. We were six points behind and we are now leaders," he said.
"It's important not to think about too many things. We have to focus on one match at a time.
"What matters is winning the league and not how we win it."
Ancelotti's night was made even better by the news that knocks suffered by Raphael Varane and Daniel Carvajal are not considered serious.
"Varane received a knock. I don't think he has any problems. His knee is fine. I just subbed him off to avoid any complications," he added.
"Carvajal's injury isn't serious. He should be fine in a few days."