The people you know best, certainly the ones who know you best, are the ones who really know how to get under your skin.
They know your hot buttons, the tiny points where your emotions run close to the surface of your character.
They know where the skeletons are hidden, the moments from your childhood that can still make you flush with embarrassment and squirm with guilt, even after all those years.
If they really love you, they will help move you on past the debris of the past.
Real friends acceptl you as youare, warts and faults and all.