Here is a single line, and it carries a whole story of one-sided effort. The speaker says their heart is "strained," a word that makes us think of a pulled muscle or an overworked body. Love has become physical labor. The speaker has been running after someone else's heart "everywhere," which suggests no place has been safe from the pursuit, and no place has brought them any closer.
What the speaker feels is exhaustion, mixed with a quiet kind of hurt. There's no shouting or blame here. The tone is tired and plain, almost like a sigh. We don't learn who the other person is or why their heart keeps slipping away, and that gap lets us imagine our own version of the story.
The title, "Harbor," adds a contrast. A harbor is a place to rest and be safe, and the speaker doesn't seem to have found one. The mood is weary and longing, with the title hinting at what the speaker really wants: somewhere to stop.