The one word you see and hear in all the books and from all the speakers on success is the word 'think'. Even in Bhagavad-Gita, Krishna first of all has to change the thinking of Arjuna before he can change his actions. Similarly, all the problems we have even in regarding to our spiritual habits, stem from our thinking. So in order to address any issues you are having you must address your thinking and change it. The big mistake devotees make is they try to change their actions without changing the way they think.