Why are my sauces splitting? Recently all my attempts at sauces are splitting and I'm not sure what's going wrong.
Tonight I tried a balsamic vinegar reduction / chicken stock / pan juices recipe to go with my lamb chops, but once again the dreaded split occurred.
My wife is patient and forgiving, but I feel like I must be missing something fundamental to get this wrong so often.

Two questions.


What could I be doing wrong to cause these sauces to split?
What can I do to recover when it happens again?


UPDATE:
The Pan juices contained a tbsp or two of olive oil, and some of the fresh herb rub I'd coated the lamb chops in (thyme, rosemary, and mint). I did not drain the pan before starting the sauce. It has crossed my mind that perhaps there was too much oil / fats in the pan at that point? 
For completeness, I should point out that I also sauteed some chopped shallots in the pan juices immediately before adding the vinegar.
There are four main reasons that a sauce splits; the fat was added too quickly, the sauce got too hot, the sauce was refrigerated and seperated, or the sauce was left standing warm too long.  The fat should be added one teaspoon at a time and blended well, or the emulsifying agent gets overwhelmed.