How does changing into his uniform turn traumatic for Ghost?

Ghost says that he normally would have changed in the bathroom, to avoid his bedroom, but that he does not want to take the chance of dropping his uniform in the toilet bowl or something, so he changes in his room, which he has not entered since the night when his father lost it three years ago. He remembers his mother pulling him, but looks down at his silver bullets, and reminds himself he is a Defender now.