The devil lives with all of us, he whispers to all people, and life is a constant battle between us,  our soul, the devil and the thoughts that cause a Muslim to be lazy in their prayer, or to not concentrate properly whilst praying. All of this is known.  It is important for us to try our best to concentrate during our prayer, take refuge by reading the Quran, to remind the soul about the devil, and to supplicate persistently and sincerely to Allah SWA to keep the whispers of the devil far away, and protect him from the soul that commands evil which urges one to do wrong, and to protect him from the devil.