In just a few lines, the speaker describes being pulled in two directions. The mind is calm and encouraging: "Do it," it says, and promises that nothing bad can happen. It sounds like the voice of reason, the part of us that weighs things up and concludes there is no real danger. But the heart doesn't listen. It "closes," like a door being shut, because it remembers what it felt like to be hurt before.
The key word is "again." It suggests, judging by the text, that the speaker has been wounded in the past and that this fear is learned from experience, not imagined. Logic can say it's safe, but feeling isn't so easily persuaded.
The mood is quiet, guarded, and a little sad. The short, plain lines feel hesitant, as if the speaker is standing at the edge of a decision, wanting to move forward but unable to. The poem ends on the fear, not on any resolution, leaving the tension hanging.