You'd probably rather spend your Spring Break at Coachella than hang out in Sonnet 133's emotional and psychological setting. Why's that? Because the speaker feels like he's trapped in some kind of freaky torture chamber. (Note to self: outdoor music festivals are way more fun than messy love triangles.)
Check out some of the ways our speaker describes the "torture" (3) of being in a bad relationship with a mistress who's been two-timing him with his best friend. First, he compares his hurt feelings to a "groan[ing]" heart that's been physically wounded (1-2). Gross. Later, he comes right out and says his mistress's heart is a "jail" cell that's got his heart in lockdown (9-12). In other words, he feels like a physically wounded and tortured prisoner who can't escape. Yikes.
We know these are all just metaphors for feeling emotionally hurt, powerless, and trapped in a lousy relationship. But, as readers, we get a vivid sense of this guy's pain and we sort of feel like we're right there alongside our speaker in that emotional torture chamber of his—especially as we watch him beg and plead and even try to compromise so his mistress will stop hurting him.
Even when we just take a quick glance at some of the key words in this sonnet—"wound" (2), "torture" (3), "slavery" (4), "torment" (8), "prison" (9), "steel" (9), "jail" (12)—we can't help but think, "OMG! Please make it stop!"
What's that? You're still having a hard time imagining what it's like to live in our speaker's psychological prison? Maybe this student's visual representation of Sonnet 133 will help.