everyone is the protagonist of their own story; or at least should be
given that, watch for these supporting characters in your own life:
a mentor is someone whom you look to as being better than you are right now, and they actively teach you how
a hero is someone whom you look up to as being better than you ever could be, and so they inspire you
a soulmate is a mirror who reflects you back at yourself, both the good parts and the bad. sometimes this person can drive you to improve out of shear spite
an anchor is a source of moral direction; they help you work out decisions, and provide a sense of rightness to what you do
an antagonist challenges you and makes you fight harder to succeed by bringing question, doubt, and a sense of wrongness to all your decisions. ironically, they secretly may be on your side and trying to help you grow
an adversary is against you; they want you to fail. this may be purely emotionless, you might just be an obstacle to them
an aggressor wants to hurt you. this is always emotional
a nemesis wants to destroy you and everything you stand for, and it probably stems from a personal grudge