This line's a little tricky, but it seems like the speaker is saying that he feels like he's not even his own person anymore because his mistress has "taken" control over him.
You know how lovers are always saying sweet stuff like "I'm yours" or "I belong to you"? Well, our speaker is sort of saying the same thing, but with a major twist. He's telling his mistress that, yep, she totally owns him, but he absolutely hates it.
Notice the alliteration in the phrase "me from myself"? It emphasizes the dude's point that he's not even his own man. It also makes it sound like he's starting to go a little nuts.
The phrase "me from myself" also reminds us that, even though this sonnet's subject is the relationship between three different people, it's really ALL ABOUT the emotions and feelings of the speaker.
Just so you know, this is pretty much the definition of lyric poetry, which is all about giving us a peek inside the speaker's brain.
So, that partly explains why our speaker is always using pronouns like "me" and "myself." (Heck. In this line, even the word "eye" sounds like a pun on "I.")
But, at the same time, we're beginning to realize that our speaker is pretty self-absorbed, even though he claims he's just really upset about his friend getting hurt in the love triangle.
So, let's talk more about the word "eye." Our speaker is dropping some more personification on us here when he says his mistress's "cruel eye" has taken him.
Technically, eyes can't be "cruel" and they can't take stuff. But two-timing girlfriends sure can, right? So, the "cruel eye" is really a metaphor for the way the harsh mistress treats our Speaker.
It's a pretty effective one, too, because it conjures up an image of a woman shooting our speaker some really dirty looks, without an ounce of pity or love in her eyes.
FYI: sonnets are full of references to mistress' eyes. When they're not being compared to suns, stars or diamonds, they're usually said to be shooting daggers or bolts of lightning at men. (Check out more on this in our analysis of "Symbols, Imagery, and Wordplay.")
And my next self thou harder hast engrossed.
So, what's worse than feeling like your cruel mistress has "taken" (5) control over you to the point where you're not even your own person anymore?
Watching her "engross" (take possession of) your best friend even "harder," that's what.
In other words, the speaker is complaining that his mistress totally owns his buddy, too, and that his friend is even more powerless than he is.
And, yeah, there's an erection joke at work here, too. (Shakespeare's sort of famous for them, especially in Sonnets 135 and 136.)
Basically, he's punning on the words "engross" and "harder." Since "engross" can mean "to make something bigger or fatter," the speaker is telling his mistress that he knows she makes his friend even bigger than she makes him.
Apparently, these two guys have compared notes or something, which doesn't really surprise us because they share everything, right?
Speaking of sharing everything, did you notice how the speaker calls his friend his "next self"?
Shakespeare's giving a shout-out to the proverb "a friend is one's second self," which was a pretty common idea in sixteenth-century literature and dates all the way back to Aristotle and Cicero.
Actually, the idea pops up all over Shakespeare's sonnets, especially in #42, where the speaker says "my friend and I are one" (13).
We all know what that feels like, right? To be inseparable from your BFF and to love them so much and to know them so well that you feel like you're practically the same person?
Obviously, these pals are super-tight-knit and our speaker really identifies with his friend.
So, now all this talk about a friend being a "next self" reminds us of lines 1-2.
Remember when the speaker talked as if he and his buddy shared the exact same love "wound" (a.k.a. a broken heart) even though the mistress had hurt each of them separately?
Now that we think about it, it seems like the speaker was also saying that he and his friend are so close that they can feel each other's pain. It's sort of like "Hey! You've hurt my friend, so you've hurt me, too."
Of him, myself, and thee, I am forsaken--
Now he says he feels like he's been totally abandoned ("forsaken") by three people: his friend, himself, and his mistress.
So, does he mean that literally? Has his mistress kicked him out of her bed completely so she can have his friend all to herself? Did our speaker's friend stop talking to him or something?
Or, does our speaker just feel emotionally distant from his friend and mistress because their relationship is so messy and complicated?
Either way we read it, we know our speaker is not happy about being "forsaken."
Notice how he positions the word "myself" right smack in the middle of his friend ("him") and his mistress ("thee")? It seems like the order of the words ("him, myself, and thee") mimics what our speaker is trying to do in this three-way relationship—he's trying to insert himself right in the middle of it.
If the love triangle is so painful, why would he want to do that? Why not hightail it out of there and protect himself? Let's keep reading…
A torment thrice threefold thus to be crossed.
So, now our speaker says that his sense of abandonment is absolutely agonizing: a "torment thrice threefold," to be exact.
Dang. That sounds pretty intense, right? Especially since our speaker busts out some alliteration (" a torment thrice threefold thus to) to get his point across.
But, wait a minute. There's something odd about our speaker's math. Let's think about this.
Since there are three people involved in this painful love triangle, the speaker feels like the he's dealing with a triple ("threefold") "torment" that needs to be stopped ("crossed").
Okay. That makes sense.
But, why does he say "thrice threefold"? Doesn't that mean 3 x 3, which (getting our calculator out) equals 9? How does he go from triple torment to nine times the amount of torment?
Is it because all three people in the relationship have triple-crossed each other and/or feel a triple pain? Does this guy just stink at math? Or, is he saying that the "torment" of being in a love triangle feels like it's multiplying completely out of control? Maybe a bit of everything? You decide.
One last thing before we move on. Our speaker is really beginning to sound like a martyr here. When he puns on the word "crossed," he makes it sound like he thinks the "torment" of being "forsaken" by loved ones is even worse than the crucifixion of Christ.
Like we said, "crossed" means to be "thwarted" or "prevented from happening." As in, he wants all this torment to stop ASAP.
Of course, a "cross" is also the kind of physical structure that people get nailed or tied to and then left to hang from...until they die a very slow and painful death.
What's weird is that he's being totally casual about making this allusion—as if comparing his tabloid worthy love life to a major biblical event is no big whoop.
FYI: the speaker makes the same move in Sonnet 44 when he complains about how bad he feels knowing that his BFF and his mistress are hooking up with each other: Both find each other, and I lose both twain, / And both for my sake lay on me this cross (11-12).