The Law of Jeans (not Genes)

If someone can explain to me how this works, I will be forever grateful:

Yesterday I wore a pair of jeans that fit perfectly for approximately 2.5 seconds.  Okay, so it was more like an hour and a half, but who's counting?  Then all of a sudden, the jeans were magically 2 sizes too big and I thought I was going to have to walk bow-legged in order to keep them up!  I mean, I get it jeans stretch.  That's how they make them nowadays.

But explain to me how the reverse is also true.  Today, I wore a pair of jeans that is a size smaller than yesterday's jeans.  So, they started off pretty snug, but I was confident that they would stretch throughout the day so that I would be comfortable in them.  No.  N.O.  If anything, they shrunk throughout the day!  Seriously, I thought I was gaining poundage by the second today!

So, the moral of the story is...I'm wearing pajama pants to work tomorrow!  If only.