This world is like a dog's curly tail, and people have been striving to straighten it out for hundreds of years; but when they let it go, it has curled up again. How could it be otherwise? One must first know how to work without attachment, and then one will not be a fanatic. When we know that this world is like a dog's curly tail and will never get straightened, we shall not become fanatics. If there were no fanaticism in the world, it would make much more progress than it does now.
It is a mistake to think that fanaticism can make for the progress of mankind. On the contrary, it is a retarding element creating hatred and anger, and causing people to fight each other, and making them unsympathetic. We think that whatever we do or possess is the best in the world, and what we do not do or possess is of no value. So, always remember the instance of the curly tail of the dog whenever you have a tendency to become a fanatic.
You need not worry or make yourself sleepless about the world; it will go on without you. When you have avoided fanaticism, then alone will you work well. It is the level-headed man, the calm man, of good judgment and cool nerves, of great sympathy and love, who does good work and so does good to himself. The fanatic is foolish and has no sympathy; he can never straighten the world, nor himself become pure and perfect.
We ought not to be fanatics of any kind, because fanaticism is opposed to love. You hear fanatics glibly saying, ‘I do not hate the sinner. I hate the sin,’ but I am prepared to go any distance to see the face of that man who can really make a distinction between the sin and the sinner. It is easy to say so. If we can distinguish well between quality and substance, we may become perfect men. It is not easy to do this. And further, the calmer we are and the less disturbed our nerves, the more shall we love and the better will our work be.
(Source: We Help Ourselves, Not The World by Swami Vivekananda)