Never meditate to the point of boredom. If you feel joy in meditation, stop meditating when the joy begins to diminish. Don’t force yourself to meditate when you’d much rather be doing something else.
At the same time, be a little stern with yourself. Don’t stop meditating altogether with the excuse that you have other things to do. Success won’t come to people who never try.
As a general guideline, I suggest you try to meditate at least half an hour twice a day — in the morning after you get up, and in the evening before going to bed. You’ll come to enjoy meditating, in time. Then you’ll find yourself meditating longer because you want to.
Make an effort to meditate a little longer once a week. In longer meditations, let periods of intense concentration alternate with periods of relaxed effort and peaceful receptivity. Until you can transcend body-consciousness, it is unlikely you’ll be able to meditate deeply for very long.
Awaken to Superconsciousness by Swami Kriyananda