..one thing you can do in all security is, before going to sleep, to concentrate, relax all tension in the physical being, try… that is, in the body try so that the body lies like a soft rag on the bed, that it is no longer something with twitchings and cramps; to relax it completely as though it were a kind of thing like a rag. And then, the vital: to calm it, calm it as much as you can, make it as quiet, as peaceful as possible. And then the mind also—the mind, try to keep it like that, without any activity.
You must put upon the brain the force of great peace, great quietude, of silence if possible, and not follow ideas actively, not make any effort, nothing, nothing; you must relax all movement there too, but relax it in a kind of silence and quietude as great as possible.
Once you have done all this, you may add either a prayer or an aspiration in accordance with your nature, to ask for the consciousness and peace and to be protected against all the adverse forces throughout the sleep, to be in a concentration of quiet aspiration and in the protection; ask the Grace to watch over your sleep; and then go to sleep. This is to sleep in the best possible conditions. What happens afterwards depends on your inner impulses, but if you do this persistently, night after night, night after night, after some time it will have its effect.
Ref: Questions and Answers 1955