The speaker begins by attacking the phrase "i love you," arguing that it gets used too easily and can mean very different things. Then the poem turns personal. The speaker loves someone obsessively, in a way that is possessive and unsettling, "not romantic or sweet" but maddening. The other person loves them differently, calmly and with care, without rereading every message or feeling the same desperate pull.
That mismatch is the heart of the poem. The speaker admits the feeling may be selfish, or may be a weakness, yet decides that real love means stepping back, since they would both be better apart. Even so, the ending shows the hurt that remains: the speaker will keep wondering whether the other person might someday say "i love you" and mean it the same way.
The mood is raw and quietly sad. The plain, broken lines and repeated phrases sound like someone thinking aloud, trying to be noble while still longing.