As abundantly mentioned before, guest posting is an extremely useful technique to build up backlinks and increase traffic at the same time.
However, although I'm not sure about that, posting the very same article on your personal website (just to quote it, for instance), too, could damage your SEO rank. Google tends to scrap similar results, especially if there are copyright licenses involved, and perfect matches could be even more subject to this. Again, don't quote me on that, but that's the only risk that came to mind, honestly.