Chelsea head coach Antonio Conte praised his team for their "incredible" first half of the season, but knows tougher tasks await with the spotlight on them.
A 4-2 win over Stoke City on Saturday saw Chelsea extend their streak to 13 consecutive league victories.
Conte's side have won 16 of their 19 league games to sit six points clear of Liverpool atop the table.
However, the Italian warned a repeat of that run was unlikely, and would grow tougher with the attention on them.
"I think that the first part of the season was incredible for us, and it will be very difficult to repeat that," Conte said.
"We played 19 games, we won 16, and drew once and lost twice. It's a great achievement for us. It's important to know it isn't easy to repeat this run.
"The second part of the season, for me, will be difficult for us, because at the start of the season, we started as the underdog, everyone underestimated us, but now the light is on us. We have to know this.
"We have to work more, harder, and to find the right solution to win every game, but it won't be easy.
"Today, we are very happy."
Willian netted a brace for Chelsea, to go with goals from Gary Cahill and Diego Costa, in their win over Stoke at Stamford Bridge.