Rav Wolbe (Shiurei Chumash) explains that the erect stature mentioned here is not a physical stature. The Torah is not referring to the proud gait of a general armed with an M-16 and decorated with a chest full of medals. The Torah is describing the feeling of spiritual elevation, dignity and greatness. This is a feeling born out of one's toil in Torah together with the performance of Hashem's mitzvos and sincere prayer.
Rav Wolbe contends that a person, who invests himself in the study of Torah, tefillos, and the performance of mitzvos, is bound to feel the spiritual sensation of walking "kommemius." This is a feeling that is a natural outcome for one who immerses himself in spirituality. He lives a life of spiritual greatness, elevated above the trivialities with which most of the world busies themselves, and he walks with dignity and the knowledge that he is following the proper path!