Answer: When you say the Name in faith, treat this nembutsu as the host and the wandering thoughts as guests. Just say the Name and let the good or bad thoughts arise and vanish, let them come and go as they please. Do not busy yourself with them, you just say the Name and entrust to Amida Buddha. There will always be something to appear into your mind and you simply cannot do anything about this. So, just entrust in Amida and let your changing mind be a changing mind.
Namo Amida Butsu