When someone decides to abandon prayers, they are also abandoning this protection. It is important to remember that this abandonment of prayers often does not happen all at once, but rather in stages. It begins by delaying prayers out of their specified times and then combining one prayer with another. Soon it turns into missing the prayer all together. Before you know it, not praying becomes the norm.
http://www.onislam.net/english/reading-islam/living-islam/growing-in-faith/452121-prayers-and-the-worst-kind-of-theft.html
