You begin wandering in the candy store, imagining a lovely unique creation. Here is a sweet yarn - puppy love! You invest in the materials (which cost twice as much as you expected) and go home to begin with a light heart. Tongue between teeth, you cast on, proud to make this beginning.
And it soon becomes clear that the yarn doesn't handle like you thought it would. You persist.
After an hour or two you notice you made a mistake way back, who knows how, when you were trying so hard to do it right. Trying to fix it makes it much worse.
Eventually you get it going smoothly. But you can see now that the whole thing is going to take many more hours work than you thought, and frankly, not be as pretty as you thought. And now that you've got the stitches down pretty well, your mind is free to tumble all around unhealthful thoughts because, face it, knitting is the same old thing, not that interesting to watch. Chopping carrots is much more interesting - at least you could cut yourself. That's why people like to watch TV or talk while they knit. It's boring. Anyway, you already have a scarf. Several, in fact.
Here is a moment of realization. You can now take the road much taken and just keep slogging along doggedly because, darn it, you said you would. You had a goal. You don't want to be a quitter. Or you can sigh and put the project aside, in that corner of your mind stacked with small guilts - all the things you really meant to do. (Don't you hope you don't find yourself on your deathbed whispering, I only wish I'd got the laundry caught up?)
Is there a middle way through this muddle? The way I see is too simple by far, and as Lao Tsu said,
The Way is simple but the crooked path is more popular.Let the project be in the past, let it flow away. Go do something more rewarding.
If that doesn't want to work, you can try thinking of the knitting as an experiment, like a first marriage. In an experiment, there is no success or failure, at least in theory. You try something and see what happens. Think of it as not being attached to the outcome. That's Zen.