If a person is driving on a very dangerous road, usually he will see signs posted, warning of any dangers on the road—such as “Dangerous curve ahead.” However, if the driver is not attentive and does not look at the signs, then he may drive right off the mountain. Thus, when we advance in spiritual life, we have to be careful about the important signs that the acaryas have left for us: “Dangerous curve ahead! Slow down! Be more attentive! Don’t fall asleep at the wheel!” All the warnings are there, and if we do not listen to them, thinking, “I am a devotee and I can just go on chanting Hare Krsna,” then we will miss the curve and drive off the mountain! Being aware of the obstacles, we should learn how to apply the proper instructions that are given to avoid those obstacles and dangers. One of the great dangers for a devotee is inattentive chanting.
LFD Vol 3,Cultivating Krishna Conciousness Pg 171, last paragraph.