I've often had problems with things like that-in fact I failed my English Comp course and haven't been back to college since due to it.
The last straw was him having us read this really bizarre story that no one in the class understood, and we were all lost. Then he gave us another that was super easy, and we were to write an essay giving it some other meaning essentially, as well as quoting things from the story to show why our theory was logical. They were both full of symbolism, but one was just a lot easier than the other because it stated several times what it was talking about.
I didn't see that one as challenging enough... so opted for the one no one understood. I finally came up with my idea after reading the story over and over and over and over and over for days on end, and wrote it all out. I was so proud of myself... then I got a big fat D- because the teacher didn't agree with my opinion or perception of what it could be about. I dropped out after asking him about how my grade was doing overall right after that.
Poems with stuff like that in them have always been hard. I did figure out a trick though... if you can "connect the dots" in a way... say, with the one you gave.
Well, the thing is about marriage mostly, so it must tie in with marriage somehow. Sift through things you've heard, stock phrases, things in movies, etc.... is rain on a wedding day ever a good sign as far as the superstitions and all go? So the rain must be a problem, and if the drops are getting bigger and bigger, then the problem is getting bigger and bigger. Since the marriage is the topic of the poem, and the raindrops are likely symbolizing a problem, then likely the marriage is going to have problems that keep getting bigger and bigger or already has problems that are getting bigger and bigger.
Does that make sense?
The words themselves make very little sense, and I would usually see them as a separate thing too, most likely, or I'd say "that would suck for it to rain that much on a day like that", but I wouldn't make that connection likely until the teacher asked... then you know the teacher is looking for some symbolic meaning, so you can begin the "connect the dot" process.
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Sorry about the incredibly long post...
"I enjoyed the meetings, too. It was like having friends." -Luna Lovegood