The Spaniard was pleased at extending Atletico's barren run in the derby and their own advantage ahead of their city rivals, but is refusing to relax just yet
The direct competitors went head-to-head in a tussle for the domestic runners-up spot on Saturday, with los Blancos securing a decisive three points thanks to Angel Di Maria's winner.
And with the Spanish champions stretching the gap from third place to six points on the night, Karanka was heartened by the team's performance.
"We knew it would be a very tense match, also because Atletico have not beaten us for so long, so we played a derby for second place," the 39-year-old told reporters after the match.
"The team played as a unit, fighting together with humility. We knew it would be an intense contest from the first minute. The whole team has done a spectacular job.
"We opted for [Sami] Khedira and Pepe today and they both had spectacular matches. We know our players and when we pick the starting XI, we know what we want to do.
"Still, we must continue doing our homework till the end of the league."
Karanka is hopeful Madrid can transfer the enthusiasm from their win to the upcoming Champions League semi-final clash with Borussia Dortmund, in the hope of overturning a 4-1 deficit from the first leg.
"We knew that the best way to go into Tuesday’s match was by playing well tonight. That is what we’ll take away; the work and effort of everyone," he added.
"For Real Madrid. every single match of the season is important. We have to enjoy what we can from this win and as from tomorrow we'll think about Dortmund."