The Blues extended their lead at the top of the table to seven points with a 4-0 win over Tottenham at Stamford Bridge on Saturday, although their rivals hold games in hand.
Liverpool and Arsenal both hold one game in hand, while Manchester City now have three games in hand over Mourinho’s men.
Were City to win all of those games in hand, they would go back to the Premier League summit on goal difference.
With everything to play for heading into the final months of the season, Ramires admits Chelsea have little room for error despite their encouraging position.
“Manchester City have games in hand and a lot can happen,” Ramires told Globo Esporte.
“We have to keep focusing on a game at a time, we can’t fall into the trap of thinking that everything is okay.
“Any slip-up could be fatal at this point in the league.
“The fans at Stamford Bridge have been our 12th player, they are creating an atmosphere which really helps our team.
“It’s hard not to be excited right now but there is still a lot to be done before we can talk about the title.”