When thou goest, thy steps shall not be straitened; and when thou runnest, thou shalt not stumble.
When thou goest, thy steps shall not be straitened - by insurmountable obstacles in thy way - i:e., in thy course through life; in all thy ordinary undertakings (Psalms 18:36).
And when thou runnest, thou shalt not stumble. As "goest" refers to the ordinary course, so "runnest" to extraordinary undertakings, wherein the believer has to put forth more than common energy (Psalms 18:29; Isaiah 40:31).