My older son picked up on one random comment by a teacher and lost confidence in math, despite numerous times that there was specific proof that he was at grade level, above grade level and even super above grade level. He was doing just fine in math but because he didn't automatically know math before being instructed in a skill he equated that with being bad.

It took several years for him to snap out of it but he eventually did. As his parents, we worked hard to fix his misperception.