The Woes of the Terrible Twos!

So lately Emma has gotten into this habit of, if she gets told no she can't do or have something, she says " PaaaaLEASE" as drawn out and whiny as possible. If that doesn't work for her (which it usually doesn't) she will proceed to cry and whine and follow me or Spencer around all the while saying PLEASE and she is relentless she NEVER STOPS.. and as of late the ONLY time she stops (and it is only long enough to tell us) is when she has succeeded in peeing her pants. And having accidents is REALLY uncommon for her, when I potty trained her she didn't have any accidents that first week and has NEVER wet the bed. To say that I am getting a little tired of these tantrums is a HUGE understatement. I don't know what I am doing wrong or if it is just that she is a two year old. It makes me feel like a failure as a mother because I can't handle my child. I have tried every thing to get her to calm down short of strapping her to the top of the van and going for a little ride. It is just all very frustrating and tiresome. If anyone has any brilliant ideas to help with my dilemma please tell me!