Atletico temporarily closed to within four points of top spot with a 1-0 home win over Leganes on Saturday, only for Barca to restore their buffer back to seven within a matter of hours.
The champions came from behind to beat Rayo Vallecano 3-1 and are now undefeated in 15 league matches.
Simeone's men have won five straight games in all competitions but, with 11 fixtures left to play, are running out of time to make inroads into the margin.
"Barcelona, since December, have been having a typical Barcelona season – always winning," said Simeone.
"We have to continue on our path, in our way, with the aim to improve. That's what motivates us each week.
"It's not easy to always win and we are competing well with fantastic players who play in various positions during a match."
Saul Niguez, a half-time substitute, provided the only goal at the Wanda Metropolitano when he tucked away the rebound from his initially saved penalty in the second half.
Simeone withdrew Antoine Griezmann at the interval and named key attackers Alvaro Morata and Thomas Lemar on the bench in a bid to keep them fresh for Tuesday's Champions League clash against Juventus.
Atletico take a 2-0 advantage into the return leg of the last-16 tie and Simeone admitted his bold team selection was made with one eye on Turin.
"It's normal," he said. "Tuesday is an important game.
"Within what we plan, we think about the game. But we try to compensate for [the Leganes] match and win it. Take it to the place where we wanted.
"The first half started a little quiet but the second, with the entry of Saul and Lemar, gave us more speed. That allowed us to win."