Quitting has its place and what I would avoid is absolutist thinking. You don't need to finish everything that you start. Sometimes you don't even want that as

Quitting has its place and what I would avoid is absolutist thinking. You don't need to finish everything that you start. Sometimes you don't even want that as a goal like when exploring or developing prototypes. The only reason that, "only start what you're going to finish" sounds good is because people tend to imagine finishing a project the way they imagined it would be when they started. There is also the story of the person that toils away year after year on a project that probably isn't going to have the outcome they intended. Then again there are people that toil for years that seem hopeless only to make a major breakthrough. There's a lot of uncertainty in the world. No one path is certain.