Imaam Ibnul Qayyim (rahimahullaah) said:

Not everyone adorned with knowledge and wisdom and is from its people; rather the people of knowledge and wisdom are those who give life to their hearts by killing the desires. As for the one who kills his heart and thus gives life to desires, then knowledge and wisdom are (merely) on his tongue (i.e. not acting upon such knowledge and wisdom). [Al-Fawaa-id: page:154]