QUOTE : The fantasy of going back in time to change something regrettable is universal but impossible. We can only understand what happened and learn to tolerate it; we can’t change the past. But when we see history repeating itself and we must choose not to interfere, that’s a different story. As Snape has found, the urge to interfere can overpower reason. The ability to overcome this urge is essential for experienced time travelers: that is, adults, parents, teachers, or anyone who has had to learn that each generation will make its own mistakes.