The speaker of this poem finds himself in something like a David and Goliath situation. You might remember David from the Bible: he’s the skinny kid from Israel who takes down the biggest, meanest giant in the land with only a slingshot. The speaker doesn’t even have a slingshot – he only has his wit, or the ability to talk circles around his enemies. He’s got all the verbal tools: apostrophe, rhetorical questions, puns – the whole nine yards.
The speaker of the poem believes himself to be a good Christian, so he's confident he’ll eventually make it to Heaven. Even so, Death is nothing to sneeze at. The speaker sounds confident, even cocky, when he tells Death that he isn’t so "mighty and dreadful." But, despite this appearance, the speaker must be quaking in his boots. He has to summon all of his courage just to keep it together. If he shows any weakness, he knows that Death will pounce all over him.
By the time the poem takes a "turn" in line 9 (as any good Petrarchan sonnet will do), the speaker really lays into Death, calling him a slave and making fun of his friends. We imagine he’s right up in Death’s grill at this point, poking his finger in his chest. Fortunately, he ends the poem on a killer line about how Death will die. This probably leaves Death scratching his bony little head. And, as is always best to do when you tell off someone bigger than you, we imagine that the speaker doesn’t stick around for when Death finally comes to again. He gets the heck out of there.