Using corn starch

I keep thinking back to a few weeks ago when I created an awesome roast in the crock pot. A decent chuck roast with potatoes, carrots, baby Portobello mushrooms, garlic, etc. Even added a few cups of burgundy wine to some water. But, when I got the rich juice after everything was all done, I tried to thicken it with corn starch straight from the box. Now, I'd seen my mother add it with cold water and then put it into juice for gravy hundreds of times growing up at home. But, I decided to be different. Mistake! Instead of a nice thick gravy for the potatoes, I ended up with "starch rice." The starch actually beaded up in the hot juice, which essentially cooked the now moist starch. I've learned my lesson.