|"Have a seat, son. Don't make me judo chop that ass."|
...says that it's better to cut a player a year too early than a year too late.
I know: there's still hope that he could improve or that he'll change back into the man you fell in love with-- but who are we kidding? He's quite alright with himself the way he is. Meanwhile, you keep getting older, fatter, and saggier as you continue to invest in the male relationship equivalent of Bernie Madoff.
Alexander the Great, while on his "world domination" tour, tried to untie the Gordian Knot, a feat never before accomplished; frustrated at not being able to untie it, he simply pulled out his sword and hacked the knot until it unraveled before walking away. [Look at your man... now back to this paragraph... now back at your man... now back to this paragraph!!!]
Some sports teams opt for a quick, clean break from a player as opposed to letting them play themselves (and the team) out. You should follow this course as well. It's two or three years in and he's all he's ever going to be, and if that's not enough then it's time for you to exit... stage left, even!
So manage your love life like a front-office guru; if it's broke don't fix it-- cut it.