Sometimes I give up on TV shows I've liked, or tried to like.
I gave up on 24 a couple of seasons ago. I came back for this season, and I like it more than I did when I gave up on it.
I nearly gave up on Battlestar Galactica. It was trying way too hard early on, the performances were forced. It just didn't work. But it got better quickly, I think. I stuck with it in large part because of Roland Moore, the guy behind the BG story, who was also one of the people behind the Star Trek: DS9 story, and that had a similar problem: weak beginning, but turned into a great epic.
Star Trek: Enterprise, on the other hand, I gave up on after the first season, and every time I went back to look again, I was sorry I did.