I am living testimony to that myself as I find myself still framing my view of the world and its inhabitants through the "spewage" that I marinated in for less than a decade. I think at times "my god, how do people ever get it completely out of their heads who spent many more years and decades REALLY IN, like 16 hours a day Sea Org in"!?!
That's basically just an extension of the old Anon-meme "What has been seen cannot be made unseen." But you can change your viewpoint regarding your experiences. You can change the levels of importance and significance they have to you, you can change the amount of influence they still have on you, you can change your interpretations of your experiences, etc.
What has been seen cannot be made unseen, but you sure can find ways to deal with it.