Faith in God and Success

Greetings and a very happy and healthy 2010. I am based in Pune, India and have a question for you.

I would like to know how we define spirituality? Do I need to believe in God to be spiritual. Due to constant struggles I have faced in my life and the loss of my younger brother in a car accident I have lost complete faith in God. I just cannot get myself to pray or have faith in God anymore

Can you please let me know if I can be spiritual in any other way? If I become an atheist or an agnostic will I be less successful in life? Are people who have faith in God and pray regularly more successful than people who do not believe in God?