Self Esteem

I have been searching for the answer to a specific question my entire adult life. How do I learn to accept and appreciate my life the way it is instead of how I believe it should be? I never seem to be content with the way things are. I cannot shake the feeling that I need to accomplish more and that what I have (materially and spiritually) will ever, no matter how hard I try, be good enough. I do not believe it is simply a question of low self esteem as someone recently suggested, but something much deeper. Perhaps you have some insight you could offer?