Why do you believe what you believe?

I know the answer that I'd like to give.  But I'm not sure it's true.  We'd all like to say that our beliefs are based on evidence and reason.  But I doubt that's always true.  How big a role do our emotions play?  How much do I believe something... because I want to?

I've noticed how what I want to believe affects how I weigh up competing propositions.  If I want to believe something then I'm more prepared to listen favourably to the arguments.  If I don't want to believe something then I'll search high and low for reasons not to.  I'll still try and rationally weigh up the arguments, but I'd be naive to think I didn't require different burdens of evidence in each situation.

So for Christians and atheists, what might it be about our beliefs that causes us to cling to them?

For Christians:
It's comforting knowing God's watching over our lives and loves us. We cannot face the meaningless of a universe without God. A desire to see justice finally triumph.

For atheists:
A desire for autonomy and not wanting to be accountable to a higher being.  To be thought of as an enlightened person who can see through all this religious bunk. A dislike for who you perceive God to be.

So do you have better reasons for why you believe something?

Or do you just want to?