Based off the song on frontman- Wilbur Soot’s EP Maybe I Was Boring, this song talks about a failed college relationship that the character now feels okay about, except for the fact that the woman is now almost married and he is missing their relationship. So he now complains.
The mention of a sextant (a measure tool used determine the angle between the horizon and either the sun or the moon) is still unknown.

Added in from a commenter: The sextant may be there to symbolize measuring the how long it’s been, or by extension, how far they’ve come