There was a time in my life when I did a lot of sewing and made most of my own clothes. One of the benefits of sewing your own clothes is you can make adjustments along the way and get a good fit.
I try to do the same thing with my knitting. Granted there isn't much fitting to do with a shawl, but when it comes to a sweater, there's plenty of opportunity for tweaking. For me the biggest adjustment is always the sleeve length. I have short arms, and I don't like sleeves that are too long. The only solution involves a bit of math and a healthy dose of good luck.
I'm working on the sleeves of my Mondo Cable Cardi. Even the shortest sleeve length in this pattern is too long for me, so it's time for some adjustments . . . number of decreases, number of rounds, number of inches.
Yesterday I worked up the numbers, and today I double-checked them. On paper it looks good. If I can get the right length on one sleeve, the second one will be a breeze.