Any action of man that hurts another being or creature or the world in general, hinders the doer in his development. This is what the pilgrimage of life means, that the primary force of the soul, as it goes from incarnation to incarnation, is set for further development. And this development progresses in such a fashion that man as it were is always putting obstacles in his own path. If this primary force were the only thing that were active — it is this very force that is to bring the soul back to the spiritual — man would need only a very short time on earth. But in that case the whole of earth evolution would have taken an entirely different course; it would also have failed to achieve its purpose.
You must not think that man would be better off if he put no obstacles in his own way. It is only by setting himself these handicaps that he grows strong and acquires experience, for it is the very eradicating and overcoming of these hindrances that will make him the strong being he must become by the end of earth evolution. It is thoroughly in keeping with earth evolution that he puts stones in his own path. If he did not have to muster the strength to remove these obstacles he would not acquire this strength at all. Then the world would be the poorer.
We must altogether disregard the good and evil connected with these hindrances and look solely at the wisdom of the world that intended, right from the beginning, that man should have the possibility of setting himself hindrances in earthly evolution so that in removing them he could acquire strength for later. We could even say that the wise guidance of the world allowed man to become evil and gave him the possibility of doing harm, so that in repairing the harm and overcoming the evil he can become stronger in the course of karmic development than he would have become had he reached his goal without effort. This is how we should understand the significance and justification of obstacles and hindrances.
Source: Rudolf Steiner – GA 107 – The Being of Man and His Future Evolution – Illness and karma – Berlin, 26th January 1909