What is Spiritual Travail?

¹⁹ My little children, of whom I travail in birth again until Christ be formed in you,

²¹ A woman when she is in travail hath sorrow, because her hour is come: but as soon as she is delivered of the child, she remembereth no more the anguish, for joy that a man is born into the world.

¹¹ He shall see of the travail of his soul, and shall be satisfied: by his knowledge shall my righteous servant justify many; for he shall bear their iniquities.