One of the absolute hardest things for me to do. One thing I've found helpful is reading "The Four Agreements" by Don Miguel Ruiz. I've read it probably half a dozen times and every time it sticks for a few months then I slide back into Ego.
The humanistic side of us makes it difficult to deal in a world where so much is thrown at us daily. It's just another reminder to give things to God and let them go!