The speaker is struggling to stop thinking about someone, and the poem's twist is in how it says so. Read the lines in order and the sentence is a little tangled: the speaker is "finding it hard to remind myself not to think of you." That's a double effort. It isn't just hard to stop thinking about the person; it's hard even to keep up the reminder to try. The thought of this person slips in before the speaker can guard against it.
The form helps carry the feeling. Each line is just one or two words, so the poem moves slowly, almost one hesitant breath at a time. The white space around the words feels like pauses where the speaker stops, falters, and starts again. The mood is quiet, tired, and a little vulnerable. There is no drama or complaint, only an honest admission that letting go isn't working. Ending on "you" leaves the other person as the last thing in the speaker's mind, and in the reader's too.