The speaker is reassuring someone, probably a person who worries about them, that they are doing all right. The first line, "I'm fine," comes quickly, but it is softened right away by "At least for now," which hints that things may not always feel this steady. The speaker also admits to having said this many times before, so the words may have started to sound like a habit or a way of calming everyone down. Then comes a turn: "But I am truly fine." The speaker wants to be believed this time.
The final lines give the reason. The speaker is okay "because you're with me today," so their wellbeing depends on that person's presence. The mood is quiet, tender, and a little fragile. There is relief and gratitude, but also a sense that the calm is temporary, and the word "today" keeps it small and honest. The short lines and simple wording make it feel like a gentle, private confession.