People have an awful lot to do with the behavior of the cattle.  I had a bull that I had used for years with never so much as a snort or shake of his head at me.  He was not a mean bull.  One day we had a visitor that had never been around our place before and he didn't happen to know much about cattle.  Every time he even got close to the fence the bull tried to kill him.  He never bothered another person, there was just something about that guy he didn't like.

Far too often we like to blame every thing else on our ability, or lack thereof, to work cattle.  If the cattle aren't working for you, back off and try to figure out if there is something going on that you can fix.  Some days it is hard to make things work right but I have a hard time believing it is the phase of the moon.  Maybe you just changed deoderant.