Someone the speaker cares about is racing ahead, and the speaker can't keep pace. The whole poem rests on one extended metaphor: speed and distance stand in for emotional readiness. The speaker says they are "1000 miles away" mentally, even though the other person believes they are standing at the door, ready to go. That mismatch is the heart of the problem.
The mood moves from patient to anxious to desperate. At first the speaker sounds hopeful ("soon i will catch up"), then frustrated at having to explain themselves, and finally afraid of being forgotten or of falling. The long, run-on lines feel like someone trying to get everything out before being cut off. The repeated plea for time, and the request that the other person turn back "a few miles," show a speaker who wants closeness but needs the other person to meet them partway. The all-caps ending reads like a shout, as if the quieter appeals haven't been heard.