At their show he said it was about the hardships of high school, and the pain and confusion. I think he's recalling all those awkward, amazing, and sad times of a first love. "Things I cannot forget" and "wish none had happened yet" are describing a loss of innocence. First love never lasts, so all those memories become painful. So I agree with passionpit, he cannot recall because it is too painful.
At their show he said it was about the hardships of high school, and the pain and confusion. I think he's recalling all those awkward, amazing, and sad times of a first love. "Things I cannot forget" and "wish none had happened yet" are describing a loss of innocence. First love never lasts, so all those memories become painful. So I agree with passionpit, he cannot recall because it is too painful.