Many studies of research scientists have shown that achievement (at least below the genius level of an Einstein, Bohr, or a Planck) depends less on ability in doing research than on the courage to go after opportunity.
A lot of people change for good. Some people just fall off. Just trying to progress in anything, no matter what you're doing, I feel like any progression you make... some people aren't gonna be around you that were around you.
You have to have the service mentality in the sense that you subjugate your own ego, and you subjugate a large part of your own life to really helping other people, being successful on their behalf.