In the moral world there is nothing impossible if we can bring a thorough will to it. Man can do everything with himself, but he must not attempt to do too much with others.
I think William Shakespeare was the wisest human being I ever heard of. To be perfectly frank, though, that's not saying much. We are impossibly conceited animals, and actually dumb as heck. Ask any teacher. You don't even have to ask a teacher. Ask anybody. Dogs and cats are smarter than we are.