We once had a session where a senior sadhu asked the lecture audience to give examples of the mind´s arguments on why not to chant properly. We got several examples:
"You slept too little" "You are too busy" "You haven´t been attentive previously, why would you succeed today?" "Surroundings are distracting, you are not going to make it" "You had bad dreams" "You are too fallen" "You are too proud"
Although we should make all the effort for all the external arrangements supportive to good chanting, chanting Japa is not dependent on anything external. I have noticed that when external things are more challenging, the mind tries to defeat me already before starting to chant...better to surrender to the Holy name instead of our mind.