Without describing his poem line from line, the overall purpose of this poem is to point out that marriages are always different. Typically a marriage won't work out when the two people are exactly the same. When he wrote "just as I am unsure of the differnce between flora and fauna and flotsam and jetsam," he's comparing two different words that have the same meaning. This can relate to marriage in which the meaning of a marriage will always be the same but always with two different lives. That phrase is considered to be an idiom. It's a metaphorical statement with a figurative meaning that's separate from its literal meaning.
In line 13, the word "Quick" is capitalized. When I first read this, I thought she was telling him to quickly get up. Then I realized it was capitalized and the word actual could be used to describe what she's saying or as his name. The title of the poem "I do, I will, I Have" I think it's significant as well. It's showing that most marriages end in divorce. It would either be his experience or the experience of many others. Another observation I made is from lines 11 through 14. He's not only showing they have two different views but the differences in being optimistic and pessimistic. The guy is seen as being optimistic. He's very laid back, hopeful and confident about things. Shes very pessimistic and things the worst and always seems to be worrying. I think with this statement he's showing the stereotype between a man and a women. Most men and women are seen in the same way that he portrayed them.
Now days marriages aren't as common as they used to be. Less people are