It's basically a load of generalisations. Our personalities are complex, we all get mad sometimes, we can all be calm other times. As with most of this sort of thing we agree with the bits we like and ignore the bits we don't. Take for example my sign Aries
Adventurous and energetic,Pioneering and courageous
Enthusiastic and confident,Dynamic and quick-witted
On the dark side...Selfish and quick-tempered,Impulsive and impatient,Foolhardy and daredevil
I'm seriously lazy and enthusiastic is never a word people would associate with me. I'm impatient but I'm not selfish in anyway. So it's basically half right.
Now lets look at Libra (i.e. ones thats not associated to me)
Diplomaitic and urbane,Romantic and charming,Easygoing and sociable,Idealistic and peaceable
On the dark side....Indecisive and changeable,Gullible and easily infuenced,Flirtatious and self-indulgent
I'm very easygoing and idealistic and a little bit indecisive (not sure about that :) ) and also flirtatious. Again about 50%.