A reason for the power of prayer.

Friesea and Wänke find one source of the power of prayer that is not supernatural: it enhances self control by buffering self-control depletion, that is, protecting from breakdowns of will. In a sequential experimental paradigm, subjects were told to watch a humorous video but stifle emotional responses (this causes cognitive depletion) and then performed the stroop task, in which they indicated the ink color of words spelling various color, with the words being either consistent or inconsistent with their actual colors. Studies have shown that this task is harder after cognitive depletion. Both religious and non-religious who were asked to pray about a topic of their choosing for five minutes showed significantly better performance on the stroop task after emotion suppression, compared to participants who were simply asked to think about a topic of their choosing. The authors suggest that people might interpret prayer as a social interaction with a deity, with that social interaction enhancing cognitive resources. Other studies have found that social interaction enhances general cognitive functioning. Here is the Friesea and Wänke abstract:

The strength model of self-control has inspired large amounts of research and contributed to a deeper understanding of the temporal dynamics underlying self-control. Several studies have identified factors that can counteract self-control depletion, but relatively little is known about factors that can prevent depletion effects. Here we tested the hypothesis that a brief period of personal prayer would buffer self-control depletion effects. Participants either briefly prayed or thought freely before engaging (or not engaging) in an emotion suppression task. All participants completed a Stroop task subsequently. Individuals who had thought freely before suppressing emotions showed impaired Stroop performance compared to those who had not suppressed emotions. This effect did not occur in individuals who had prayed at the beginning of the study. These results are consistent with and contribute to a growing body of work attesting to the beneficial effects of praying on self-control.