Why does she keep trying?!

Dock has an obsession about being on the kitchen counter.  Especially if I'm doing dishes, so I try to do them when she is stowed away in her room eating. (That is so Mace doesn't bully her out of the way and get her food, poor girl will starve)  Today was no exception.  I was getting coffee ready, and had to move a few dishes into the sink.  Sure enough, there she was, ready to hop on the counter.  Due to her bad knees, she doesn't have a lot of strength to get up, so I have a little mat for her to give her some foot traction.  Despite that, she still doesn't make it sometimes, and lands hard on her already delicate frame.  You think she'd learn that she doesn't always make it, and it hurts.  But she still tries, and makes it about 75% of the time.  This morning though, she must have some weakness as she tried 3 times before I made my way into the coffee maker.  (You can't help but hear it when she falls).  Getting the brew started, she jumped again, and would not have made it had I not caught her back end and hoisted her up.