Because a thorn isn’t natural to our body, it gets rejected by our system even if we don’t get it out manually. Eventually, often with quite a bit of pain, it will leave the body.
Similarly, if there is an untruth, say an old belief or thought or emotion that no longer feels natural to us,it too shall rise to the surface in order to released.
When you change your context from the victim, persecutor,rescuer paradigm to the fully personal responsibility paradigm, inevitably old emotions, charges, beliefs and behaviours will come up and challenge our new view.
Remember to see it for what it is. None of it is who you are, its simply the process we go through as we evolve and get to know ourselves on a deeper, more meaningful level.