How weird. I used almost exactly the same language to someone about the time you wrote this. Must be a cosmic ray.
CSI: Las Vegas when I fell asleep in the middle of the second or third episode after Grissom left.
CSI: Miami after the space tourism episode, though I should have quit sooner, right after the “wedding-veil-ruined-the-bumper-mounted-remote-controlled-pistol’s-laser-guided-aim-and-killed-the-bride-instead-of-the-intended-victim-in-the-front-row” episode.
CSI: NY after Stella left. Say no more, say no more.
24 after marathoning the final and first three seasons. The one where Jack Bauer was stabbed in the gut twice, stitched up without anesthetic, shot in the chest with a Kalashnikov (whose bullets would not be stopped by a Kevlar vest), and then took a 9mm round in the shoulder and was still able to go on a rampage through the tunnels of New York was the one that pushed me over the edge.
White Collar. I quit after 3 or 4 episodes. I wanted to like it since I guess it’s an updated It Takes a Thief and the lead actor is yummy, but the wife of the FBI guy treats him like he’s two years old. She scolds him and orders him around and he obeys her every command. blech
Star Trek Voyager after about the 4th season, though I had only watched it periodically anyway. It got to the point where every episode was bland, there was no attention paid to the premise of the overall story, and the characters no longer held my interest.
The remake of BSG toward the beginning of the third season when it became clear that the writers had no plan, and neither (despite assurances) did the Cylons. I did finally go back and watch it on DVD and felt the last 10 or so episodes were just a mishmash of trial and error plot ideas. A shame, because much of the show was very interesting.
When one of the lead actresses has plastic surgery, I find that’s the kiss of death for me. My mind is forever wandering away from the plot line. I’m trying to identify what tiny change is registering that I can’t seem to put my finger on what it is exactly. Then I find I’ve totally lost the story line. It’s terribly distracting.
Once Upon a Time, sadly, because I loved the premise. Emma is supposed to be a smart, savvy woman. The first time we see her, she’s a bail bondsman who has the foresight to get the car of the person she’s chasing booted before she meets him for a “date”. But she *believes *Storybrooke’s newspaper editor when he tells her he’s turned on the mayor, even though it’s been incredibly obvious that he’s the mayor’s weasel. I could not reconcile a woman stupid enough to do that with the woman who’s a successful bail bondsman. Just couldn’t do it.
I half-watched Glee the first part of the third season, but I think what caused me to stop really watching is the end of the 2nd: they made it to nationals and they hadn’t even written their songs? And then they get 12th place? And the teacher wasn’t fired for that? I had already suspended disbelief with that show, but that was the final straw.
Oh, and Mr. Shuester has a chance to be on Broadway and no one was legitimately excited for him? It’s not like it’s the 1800s where you’d never see the person again.
ETA: I stopped watching Breaking Bad after the third episode. Although I could easily see how it was a well-made show and why people liked it, it was just way too dark for me.
Yeah, she should have never climbed on top of that doc.
mmm
True Blood - Ok, so nobody should expect anything remotely intellectual or cerebral from this show because, well because it’s “True Blood.” But after a few years of becoming impatient with the show piling on one go-nowhere storyline after another, with ever more ridiculous supernatural creatures, I finally got to an episode in which Sookie and her brother go to a fairy nightclub, Sookie starts shooting white light into the sky, Lafayette gets his mouth sewn shut by some ancient Inca witch-doctor ghost, there’s stuff about a bunch of redneck werewolves, and all the vampires are giddily stoned on some weird ancient blood, and during their wanton massacre at a New Orleans bar, a naked vampire goddess appears before them, and…I actually screamed out loud “This is so fucking STUPID it makes my brain hurt!”
Don-You worry about giving up on Mad Men?
I gave up on Falling Skies when I realised I had six episodes saved up and I kept putting it off. It’s really just a soap opera with a lot of gruff people with hearts of gold being entirely disorganised and hating each other. There’s no entertainment value in that. Walking Dead is the same, which is also why, after giving it two chances, I am no longer watching.
I gave up on *Weeds *when she told her cartel boyfriend she was pregnant with his baby. I don’t remember if that was the end of season 4 or 5, but at that point I realized the story had become just too ludicrous to follow.
Nope! 
Ready for the new season - light my cigarette, and serve me up a Kentucky whiskey Old Fashioned laced with LSD (just the way Roger likes 'em!) and let the new season roll!
But to keep on topic, I’ll also mention that I have given up on “Walking Dead” just recently. What’s most frustrating about this show is every once in a while, there is an episode that gives a brief glimmer of how good the show actually could be. But lately I’ve come to the conclusion that TPTB simply don’t give a damn about producing even a good show. Why bother developing strong, multifaceted characters and pitting them in engaging stories when you simply just have a bunch of zombies lurch into view and get shot / sliced / pummeled in the head and then have brains driblble all over the place?
I gave up in Shameless the moment the alcoholic dad head butted his son (10 or 12 years old?). Literally – I turned off the show within like 30 seconds of the scene and never went back. Sorry, I just can’t see a show that portrays a parent physically abusing his young son as a comedy.
I started watching that show around the time that Dr. Carter was stabbed. I washed my hands of the show when Dr. Romano was killed. To me, Dr. Weaver should have been the one to go, especially when she decided to fire my favorite doctor. I was all about Dr. Dave Malluchi. 
God bless you always!!!
Holly
The Facts of Life after they fired Molly Ringwald and that blond girl with the pigtails. I was 11.
/slowclap
Star Trek: Voyager lost me with the Warp 10 turns you into a salamander episode.