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.
Most of our pocket wisdom is conceived for the use of mediocre people, to discourage them from ambitious attempts, and generally console them in their mediocrity.