He and a fellow psychologist at the University of Miami, Brian Willoughby, have reviewed eight decades of research and concluded that religious belief and piety promote self-control.
The intrinsically religious people have higher self-control, but the extrinsically religious do not.
Quotes from here.
While I don't buy much of this type research, perhaps some secularists may find some of the findings interesting.
For discovery of the fountain and fruit of self-control, try reading Galatians 5. :)