The speaker of this sonnet says he's completely bummed and that he's been bawling his eyes out over his pathetic life and all of his misfortune. He says he's all alone and feels alienated and unsuccessful. Heck. Even God is ignoring him and won't return his phone calls.
He says he wishes he was rich and had something to hope for. Also, he totally wishes he was good looking, popular with friends, and talented like some other dudes he knows. But he's not, which is why nothing seems fun anymore—not even the stuff he used to enjoy doing.
Just as our bummed out speaker is thinking about all the stuff he used to really dig, he suddenly remembers a special person in his life and his mood begins to shift in a big, dramatic way. The mere thought of this unnamed mystery person makes our speaker so unbelievably happy and hopeful that he feels like a bird (a "lark," to be exact) that rises up and sings to the heavens.
Finally, our speaker concludes that, hey, life is pretty great after all. Even though this unnamed person isn't exactly around right now, just thinking about his or her "sweet love" makes our speaker feel like the luckiest guy ever—so lucky that he wouldn't trade places with anyone else for all the money and power in the world.