"When things were going well, we were happy with him, but when things are not going well, he could be unhappy," said Jol on the eve of a vital festive programme.
"He's almost used to winning games with the clubs where he was [Tottenham and Man United], so we have to talk to him and players have talk to him, and he has to do the same.
"He's got to put in the same sort of attitude or work-rate that he always did. When he does that, there's no problem, but he is certainly a player we have to keep on his toes to do well for us."
Jol added: "We were very happy with him the first couple of months and now he should be happy with us as well, so we have to keep each other happy."