As you know, the lunar cycle lasts about one month: the moon waxes for fourteen days and wanes for another fourteen, and this alternation affects and changes many things in nature and in human beings. We can say that the period of the waxing moon is a time for activity, whereas, on the contrary, when it is on the wane, the emphasis is on somnolence, oblivion and rest. Those who do not know that these natural rhythms exist might be worried by the changes that they feel in themselves while the moon is on the wane. There is no need to worry; the important thing is to take care not to use up all one’s reserves.
Even if the lucidity, intensity and efficacy that we bring to our work while the moon is on the wane are not as great as when it is waxing we can still continue something that we have already begun. If you inaugurate some important work or activity, on the other hand, it is more likely to succeed if you wait until the waxing moon offers more favorable conditions. And if you want to terminate something, it is better to do so while the moon is on the wane.
So as you see, it is possible to put each phase of the lunar cycle to good use for a specific spiritual work. Suppose you want to increase your will -power or improve your health, to have greater wisdom or light: wait for the first few days of the waxing moon and then, at night, look at the moon, raise your right hand and say, ‘Just as the moon is filling out in the heavens, may my whole being be filled with health and vigor- or with light or love, etc- so that I may become a true servant of God.’ Repeat this formula three times.
And when the moon is waning, you can ask for just the opposite: ‘Just as the moon is waning, may such and such a weakness in myself decrease and disappear, for the glory of God.And this. too, you repeat three times, with your right hand raised. If you do these exercises regularly and with conviction you will get results.
The moon has great power over matter, that is why it has an important role to play in every kind of realization or materialization. Whenever you want to undertake something new, to carry out or, alternatively, to put an end to a project of some kind, you will always get better results if you know how to use the influence of the moon.
Omraam Mikhael Aivanhov The Book of Divine Magic