There are fears in relationship, fears of uncertainty, fears of the past and the future, fears of not knowing, fears of death, fears of loneliness, the agonizing sense of solitude. You may be related to others, you may have a great many friends, you may be married, you may have children, but there is this sense of deep isolation, this sense of loneliness. That is one of the factors of fear. There is also the fear of not being able to fulfill. And the desire to fulfill brings with it the sense of frustration, and in that there is fear. There is fear of not being able to be absolutely clear about everything. So there are many, many forms of fear.
J. Krishnamurti/On Fear, p 62