Really, really, really good. As Peejay pointed out, the second verse doesn't quite match up with the first. Unless something that improves the "story line" comes to you, don't mess with it. These things are best cleared up when the music is added because the music is going to demand some changes anyway.
The chorus had this wonderful, vague, denial thing happening. The singer/protagonist/narrator contradicts him/herself exactly like human beings in denial do. He/she wonders who is to blame, then lets it slip that he knows neither of them (and both of them) are.
On so many levels, the emotions are mixed. There is a surface level "Oh God NOOOO we've drifted apart." And well below the surface, there is just a tiny ripple of .... perhaps RELIEF.... that they have drifted apart.
Blame is accepted and denied all at once. Blame is assigned, then rescinded. This just TOTALLY captures a break-up that is probably the best thing for both parties concerned.
Not that you necessarily MEANT that when you wrote it. But all that is in there.