Oh man, this is soo true and on point, took the words right out of my mouth! My EXACT feelings in regards to being a Step Mom.
Step mom. I can only say I tried my best - even in times of conflict with my mother in law. It is such a hard balance of doing too much and not enough. Don't always believe your husband and mother in law about the ex-wife/mother. Remember they divorced for a reason!
A successful stepmother worries less about replacing their biological mother and more about being the BEST bonus mom she can be. She knows she is unique and special on her own. She doesn't need to compete with anyone else.