The speaker is caught in a low, tangled state of mind. They admit their thoughts have been crowded and heavy, yet they still feel empty, a odd mix that sets the tone early. They can't quite remember why they were angry, which suggests the anger came from something deeper than a single event.
In the second and third stanzas, the speaker describes themselves as complicated, easily irritated, and capable of sinking very low. They question why they kept trying, then insist that saying "I don't love you" would be a lie. The poem doesn't say who "you" is, so it could be another person or even a version of the speaker.
The last stanza turns inward. The speaker says they are the thing they despise and the person they hate most. Still, the ending leaves a small opening: maybe they will rise, and maybe they will reach the coast. The mood is heavy and honest, but a thin line of hope runs through it, carried by the water imagery of sinking, rising, and shore.