The speaker is looking back on a relationship, probably a friendship or a romance, with someone who stood by them at a hard time. The first three lines are a list of thanks, each starting the same way: "i thanked you." The repetition feels steady and sincere, almost like someone counting up everything they owe. The third line, "caring when nobody else did," suggests the speaker was lonely and that this person was the only one who showed up.
Then the last line turns everything around. "But i never apologised for leaving you" admits that the thanks were not enough. The speaker took the support and then walked away, and they know it. The word "never" makes the guilt sound ongoing, as if it still weighs on them.
The mood is quiet, regretful and a little raw. The lowercase letters and plain wording make it feel like a private confession rather than something polished.