Technically speaking, Shakespeare’s Sonnet 137 doesn’t have a title; we just know it by its numbered position in a series. We also know it by its first line, though, which is used at times in place of the title.
So, let's look at that line shall we? We shall! Check it out:
Thou blind fool, Love, what dost thou to mine eyes,
Nice work, Mr. S. You've set up some major issues that will carry forward into the poem, and all in that very first line. For example, here we see the speaker blaming the divine being Love for messing with his vision. That announces, right off the bat, that the speaker is not blaming himself for the problems he's about to go into: namely, his lack of vision.
Now, what do you think about that? Sure, perhaps his unfaithful lover may have been a masterful sneak at being on the down-low, but even then, the speaker is not blaming her really (we assume that it's a her, though scholars might argue this point), either. He's blaming Love, which is an abstract entity. Think about that for a second. By blaming Love—some imagined chubby baby with a blindfold and a bow and arrow—is the speaker avoiding blame altogether? It would seem that he'd be more direct here, but instead he blames this higher power instead.
This sets up the kind of round-about discussion that carries forward in the rest of the poem. Mainly through metaphor, the speaker bemoans his lover's cheating on him, but he leaves out all the gory details. Perhaps this experience is just too raw for him. Perhaps he blames Love because he simply can't accept that his loved one is truly to blame for his betrayal.
Still, even he admits that he should have seen it coming. Right in line 1 we get another major theme of the poem: vision. The speaker frames his betrayal as poor eyesight—he simply didn't see what kind of person he was in love with. The poem, then, becomes a catalog of the ways in which his eyes failed to alert him to the truth. So, in this way, perhaps the speaker blames himself for not being more aware of what was going on.
One thing is clear—and it's clear right from the start in this first line—the speaker spends a lot of effort in avoiding blaming his loved one. You might see that as deluded (wake up, dude!), romantic (you still love her, man), or some combination of the two. Like many aspects of love, this poem's first line leaves us with more questions than answers.