I rarely stop watching/reading/playing something, mostly because I always have the nagging feeling that just the next episode/the next page or the next hour of playing something turns the ship around. But if you really aren’t enjoying something, the best thing is to stop doing it. I already tried watching Farscape in the past two times and never managed to watch further than the first season.
This time I came as far as the fourth season (episode 9), but watching the show felt like such a drag that I had to stop. Too many boring and predictable plotlines, and the focus on horror and mostly ridiculous mystical elements didn’t help. I do wish I had the energy to finish it, but I’m fine not knowing how it all ended.