For those working in Krsna consciousness, there are simply not enough hours in the day to serve Krsna. There are always activities, engagements both day and night, which the student of Krsna consciousness performs joyfully. That is the stage of real happiness — constant engagement for Krsna and spreading Krsna consciousness around the world. In the material world one may become very tired if he works all the time, but if one works in Krsna consciousness, he can chant Hare Krsna and engage in devotional service twenty-four hours a day and never get tired.

(From “The Perfection of Yoga,” by Srila Prabhupada)