The speaker insists she can be alone, and she says it again and again. She can survive pain alone, and she can even feel happiness alone. Then she lets someone in, but only a little. Having this person around is "comforting," and it's "nice to not be by myself." The words are warm, but they are also mild and careful, as if she is measuring out how much she will admit.
The turn comes in the line "but don't overstep your place." Here the poem gets firmer, almost like a warning. She closes by repeating her opening claim, so the poem circles back to where it started. The signature "- fear" is the key to the whole thing. It suggests that all this independence may be a shield, and that the speaker is afraid of depending on someone and being hurt. The mood is guarded and quietly tense: short lines, plenty of white space, and a voice that sounds calm while trying very hard to stay in control.