All great success and achievement is preceded and accompanied by hard, hard, work. When in doubt, 'try harder.' And if that doesn't work, try harder still!
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.
Your success in life and work will be determined by the kinds of habits that you develop over time. The habit of setting priorities, overcoming procrastination, and getting on with your most important task is a mental and physical skill. As such, this habit is learnable through practice and repetition, over and over again, until it locks into your subsconscious mind and becomes a permanent part of your behaviour.