In May, I decided to design my own sweater, a top-down, raglan pullover with an asymmetrical neckline.

Coming up with ideas for colours and shapes was easy. Starting was difficult, mostly because of the top-down, seamless technique. In a conventional handknit garment, the individual parts (i.e. the front part, the back part, the sleeves) are knit separately and joined later. If you have designed a sewn garment, it's generally not hard to imagine how you should begin knitting the parts of a sweater. But when you knit a top-down seamless sweater, you're making all the parts simultaneously, a little bit at a time. If one part starts goes wrong, the whole thing needs to be torn back.
This morning, I am frogging 4.5 inches of sweater (in other words, the whole thing).

Two things can go wrong right from the start. Your proportions could be off (this happened with my
garter stitch swing sweater) or you could start shaping the neckline incorrectly. I was lucky enough to figure out good proportions from the start, but I keep messing up the neckline. I've torn it back three times already. It look me a lot of thinking to realize that the neckline should look like this, roughly speaking:

(You know, if the sweater had been cut up the sides and up the insides of the sleeves.)
And now I just need to figure out how to achieve that angled line and rounded corner. I think I've figured it out (but only after hours of knitting a neckline that would join somewhere near my my solar plexus).
Lesson 1: I should try testing the rate of decrease on a swatch first, to see if the neckline will be too shallow or too plunging. I should then try to picture that angle on my body. I don't know if this will work or not, but it's less effort than knitting 4.5 inches of yoke only to rip it out the next morning!
Lesson 2: Tearing back is annoying, but it's not the end of the world. In fact, it seems to be a fundamental part of the process of making something good. Camilla Engman is an illustrator who designed two very cute amigurumi animals for Debbie Stoller's
The Happy Hooker. In a 2006
Whip Up post about her process for creating original amigurumis, she said "I will have to start with admitting I’m not a very good crocheter, I’m good at undo, redo, undo and redo. And maybe I have a good eye for what’s cute."