Chelsea won 4-0, with Palmer missing a hatful of chances on the night.
"He has to continue to work, continue to be happy, continue to laugh the way he does," Maresca told BBC Match of the Day.
"It is normal to go through a moment where you struggle to score but it doesn't matter. Just continue and you are going to score many goals."
Palmer hasn't scored in his past seven appearances.
But Maresca says: "It is how you react. He is reacting perfectly. He is smiling and he is happy. We have no doubt he will score more goals.
"He's a human being. All human beings, all big players, all the normal players, big club, big manager - we all go through a bad moment.
"Even if he is young, he shared time in a big club and he knows that all the big players go through moments like this."