Plain Sailing Weather Lyrics

Lyric discussion by getupkid4uga 

Cover art for Plain Sailing Weather lyrics by Frank Turner

One of my favorite lyrics in a long time. Clearly about making mistakes in a relationship, but my main question is if the phrase "Things got fractious, and I felt faithless, at that moment just before the dawn when everything falls apart" refers to an affair.

The last stanza is really powerful; I feel like it's insinuating a disconnect between the two of them that doesn't allow him to actually say he's sorry, making it impossible for them to coexist. So even though he wants "forever", she still doesn't truly accept him as he is.