Sometimes when a child struggles to accept a stepparent it has more to do with staying in contact with their biological parent than it does necessarily rejection of the stepparent. If you can keep that in mind then maybe you won’t take the rejection so personally. The Apostle Paul spoke lots of truth but lots of people rejected him. What kept him going was feeling his heavenly Father’s approval even when he didn’t have it from those around him. That’s a good prescription for stepparents, too.