P.S. I think religious/spiritual belief is utilised for several reasons:
1. empathy for a persons situation and wishing to help them through it
2. affecting other people so that they support your belief system (and thus way of life) e.g. physically weak people would naturally support pacifism as they gain more power from using other methods.
3. control of others
4. insight which you wish to share (or be confirmed) by others.
Also, we have to remember, that what we think we think (what our concious mind is doing) may only be a way of justifying our own selfish actions in a way in which we can portray ourselves as unselfish.