Barth, CD I/2, p.277

Further, we have to note that this following is distinguished from an arbitrary action, like imitation, by the fact that it is conditioned by the call of Jesus.  It is therefore a Messianic gift. The individual who decides ("Lord I would follow thee") to tread this way on his own initiative, at once proves that he is not suited for the kingdom of God (Lk. 9:61f.) Finally, the frequent inter-relating of the idea of following with the idea of self-denial ought also to prevent us from thinking that this is the kind of formation and direction which a man can undertake of himself.

Strong words.