Srila Prabhupada always said that in order to have a fixed, nice sadhna, we have to become Serious and Sincere, along with these two, Service and Surrender. If you are very Serious and Sincere about performing sadhna, then you will be getting up very early, may be 4 or 4:30, you take bath and then you start the service – chanting, deity worship or any other service to Krishna.
Two other things, Surrender and Service. If you are surrendered to the process or sadhna bhakti, if you are surrendered to Lord and His devotees, then that will make you rise early for sadhna.
Like when Lord Chaitanya visited Kurmakshetra, one illiterate Brahman who didn’t know how to read but was reading Bhagavad Gita and crying, crying and crying. Then Lord Chaitanya asked the Brahman, “Why are you crying?”.
The Brahman said that “My Guru said that please read Bhagavad Gita everyday but I am illiterate, I don’t know how to read but by looking at a picture in the front, where Krishna is driving Arjun’s chariot, the Supreme Personality of Godhead is trying to serve, I could not hold myself and I cried.” So there was Sincerity and Surrender, he was Serious about reading, even though he didn’t know how to read.
If you are Serious, Surrendered and very Sincere, then you can make a resolution and stick to it. We should not listen to our mind or intelligence or anything, tell them that “I have sold you to my Spiritual Master”.