Sri Chinmoy: The power of a person's prayer depends on the consciousness of the individual. If the consciousness of the individual is high, then his prayer will be more potent. If his consciousness is not high, even if it is his birthday, then it will not be potent.
Some seekers are clever or wise. Over the years they have observed that they do not make any progress on their birthday; instead, they go downhill because often the hostile forces attack on that day. So five or six days before their birthday, they pray and meditate with utmost sincerity, love and devotion. In this way they accumulate inner wealth. Then, if the hostile forces attack them on their birthday and their consciousness descends, if they are not feeling spiritual at their birthday party, it is not so bad because they have already earned and received so much.