You may not be sleeping well in the night. Very few people are sleeping well, so when you have not slept well in the night you are a little tired during the day. If that is the case, then do something with your sleep. It should be made deeper. Time is not much of a question — you can sleep for eight hours, and if it is not deep you will feel hungry for sleep, starved — depth is the question.
Every night before you go to sleep do a small technique, and that will help tremendously. Put the lights off, sit in your bed ready to sleep, but sit for fifteen minutes.Close your eyes and then start any monotonous nonsense sound, for example: la, la, la – and wait for the mind to supply new sounds. The only thing to be remembered is those sounds or words should not be of any language that you know. If you know English, German, Italian, then they should not be of Italian, German, English. Any other language is allowed that you don't know – Tibetan, Chinese, Japanese. But if you know Japanese then it is not allowed, then Italian is wonderful.
Speak any language that you don’t know. You will be in a difficulty for few seconds only for the first day, because how do you speak a language you don’t know? It can be spoken, and once it starts, any sounds, nonsense words, just to put the conscious off and allow the unconscious to speak.... When the unconscious speaks, the unconscious knows no language.
It is a very, very old method. It comes from the Old Testament. It was called in those days glossolalia and a few churches in America still use it. They call it “talking in tongues”. And it is a wonderful method, one of the most deep and penetrating into the unconscious. You start by saying “la, la, la,” and then anything that comes you go on. Just for the first day you will feel it is a little difficult. Once it comes, you know the knack of it. Then for fifteen minutes, use the language that is coming to you, and use it as a language; in fact you are talking in it. This will relax the conscious so deeply.
Fifteen minutes – and you then just simply lie down and go to sleep. Your sleep will become deeper. Within weeks you will feel a depth in your sleep, and in the morning you will feel completely fresh.
Osho, Yoga: The Mystery Beyond Mind,