I think it might be about a long distance relationship. One person is trying to "keep it (the other person's cheating) quiet", a secret. The narrator cheats obviously, and sends "letters and souvenirs" that make it obvious to anyone. I think the narrator might be trying to get the other person to break up with her, but they still "try (their) best to make it matter" and convince her not to cheat on them. I'm really just agreeing with thatfangirl here, only with the long distance part.
I think it might be about a long distance relationship. One person is trying to "keep it (the other person's cheating) quiet", a secret. The narrator cheats obviously, and sends "letters and souvenirs" that make it obvious to anyone. I think the narrator might be trying to get the other person to break up with her, but they still "try (their) best to make it matter" and convince her not to cheat on them. I'm really just agreeing with thatfangirl here, only with the long distance part.