Someone has left, and the speaker still cannot get a moment's peace from them. That is the quiet joke and the quiet ache of "mind of mine": a person who is no longer present behaves, inside the speaker's head, like a tenant who never handed back the keys. The poem never says who "you" is. Judging by the smiles and the "lingering touch", it is probably a former lover, but the text leaves the relationship open, and that openness lets many readers slip their own person into the gap.
The opening line, "There you go again", sets the tone. It sounds like a sigh, half exasperated and half fond, the way someone might speak to a person who keeps wandering into the room. Then the poem gives the intruder two different ways of moving. First "you" is "running through my mind", which is fast, careless and noisy. Two lines later it becomes "tiptoeing across my thoughts", which is soft and almost apologetic. The two verbs don't quite agree, and that is useful. The memory seems to arrive however it likes, sometimes as a rush and sometimes as a whisper, and the speaker has no control over which. The phrase "like you belong here" adds the poem's first hint of trespass: the visitor behaves as if they have a right to be there, and the speaker notices.
What the visitor leaves behind is odd and tender: "your smiles / for me to think about". Smiles become objects, like things dropped on a doorstep or forgotten on a table. They look like gifts, but "to think about" turns them into a task. Memory here is generous and burdensome at once. The "lingering touch" does something similar. The touch is physical, yet it is "tracing the imaginary / of words you played with", so it moves over invented things rather than skin. The phrase "the imaginary" is grammatically strange, since "imaginary" is normally an adjective, and the strangeness suits the idea of a private world made of shared invention. "Made up, out together" is just as compressed. "Made up" suggests stories and games, while "out together" suggests outings or being seen as a pair. The line seems to hold both, and its broken syntax makes it sound like a half-remembered phrase.
The central image arrives near the end: "building a home for yourself". The title already tells us the mind is the speaker's own ("mind of mine"), and now someone else is putting up walls inside it. The word "uninvited" is the sharpest in the poem, yet the speaker has not actually changed the locks. Nowhere does the speaker say "leave". The poem complains about the occupation without ever trying to end it, which may be its most honest feature.
The last line holds a small paradox: "uninvited, you stayed / long after you're already gone." The tenses collide, with "stayed" in the past and "you're already gone" in the present. That collision is the point. Staying and going happen at the same time, because the person has left the world of the speaker's days but not the world of the speaker's thoughts.
The form supports all this. There is no rhyme scheme and no steady meter, only short, conversational lines of two to four beats. A few echoes surface anyway: "mind" returns as "behind", and "leaving", "lingering" and "long" share a soft l-sound, like the loitering they describe. More importantly, the whole poem is one sentence. The lines are joined by enjambment and a few commas, and the first full stop comes only at the very end. Nothing interrupts the stream, so the reader experiences how a thought about someone can run on without a natural place to stop. The lack of capitals in the title and the plain diction keep it intimate, like a thought rather than a performance.
The poem is significant for how much it makes of so little. It uses no grand declarations of grief. It gives a small, recognisable experience, being visited by someone who isn't there, and finds a precise image for it. For students, it shows that a poem can be powerful through plain words, a well-chosen metaphor and a form that behaves like its subject.