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.
Be true to yourself, help others, make each day your masterpiece, make friendship a fine art, drink deeply from good books - especially the Bible, build a shelter against a rainy day, give thanks for your blessings and pray for guidance every day.