Measuring Success

I have been confronted with the subject of success a great deal recently and this has led me to wonder a bit about how I define success to begin with. A few times over the past few years I have revisited these thoughts and I do realize that perhaps what I define success as will be ever changing, but at the moment I am unsure of how I feel right now. Is it a measure of my dreams coming true, or of reaching a certain monetary level, or a passing of multiple milestones in life that I want to pass... Do I consider myself already successful at some aspects and failures at others, or is it a more straight forward then that. I do know that I feel success can be fleeting...it can go away once achieved just as fast as it came. Will I never feel successful because it creeps up you when you least expect it....like the 5lbs gained over the winter that goes unnoticed until you try on a bathing suit...Will I ever feel as though I have success because I will always be reaching higher and moving onto the next definition while my previous one is conquered? How do I stop the nagging in my head that I must work harder, better and longer then the day before if I have no idea what I am trying to accomplish...ahhhhh...tomorrow is another day....