I don't buy clothes without trying them on. I swatch. I have taken measurements from a favorite, similar-fitting garment, to determine which size to knit. Sure I substitute yarns, and maybe my gauge isn't spot on, but it's "close enough." So why do I now have two sweaters that are too tight, and one that's probably too loose? I attribute it all to a mild case of body dysmorphia (and an aversion to the math that is most likely required to successfully reknit the sweaters in question).
And yes, I do crave the result enough to figure it out. (Eventually.) =;)