What is it?!

I wonder what's wrong with me? The 'Back to School Vest' has now been frogged twice; first the bottom part (the ribbing was too narrow for my waist) and yesterday I had to frog the upper part, as well (that was too wide for my chest). But watching Gary Grant and Ingrid Bergman in "Indiscreet" did sort of make it all allright, I didn't mind that much spending 2 hours knitting for nothing..
And those Autumn mittens as well, I decided to frog them and start with a smaller stitch count - thus leaving out part of the pattern, but what the heck... as long as it's fits, yeah?

Now, what could be the reason for these sudden size problems? Could it be that ancient enemy of the inspired knitter who's ready to plunge into a new project head first, and who just picks up the needles and gets goin', regardless of the instructive sentence in all knitting patterns which tells you to ....

Check your gauge, girl!