Friends don't like change
I've changed in the last few years. Some friends of mine resisted it and hated it, which was natural. Friends like you the way you are, and they like the dynamic between you. But I am happier now than I once was, and I'm still on good terms with those who were closest to me.
Hugh at Gaping Void has related thoughts, focused on business (via I Will Teach You To Be Rich.