The word guru means "one who is heavy," so heavy that he can never be shaken. A guru is a person who is so deeply established within himself that no force on earth can affect the complete love he feels for everyone. If you curse him, he will bless you; if you harm him, he will serve you; and if you exploit him, he will become your benefactor. It is good for us to remember that the guru, the spiritual teacher, is in every one of us. All that another person can do is to make us aware of the teacher within ourselves.

Eknath Easwaran, The Bhagavad Gita for Daily Living: Volume 1