As you know by now, spiritual life is not a mechanical process. We do not advance just by "punching the time clock" to report for devotional service. Krishna conciousness is a way of life, from morning to night, and even while we sleep. It's true that we may fix a time for Krishna conciousness, but we must use that designated time to its full potential. It is a time to establish the right motive for everything that we do, and to pray for strength to follow that motive.
Collected Letters to Friends and disciples Vol 4, Pg 108, 2nd paragraph.