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.
Take up one idea. Make that one idea your life - think of it, dream of it, live on that idea. Let the brain, muscles, nerves, every part of your body, be full of that idea, and just leave every other idea alone. This is the way to success.
For a warrior, nothing is higher than a war against evil. The warrior confronted with such a war should be pleased, Arjuna, for it comes as an open gate to heaven. But if you do not participate in this battle against evil, you will incur sin, violating your dharma and your honor.