The appearance of chiasm brings to light words, phrases, or subjects that are either synynomous or antonymous in meaning. As is the case in Psalm 1.6: just as the godly and the wicked are antonyms, to say that there is a way that leads to destruction is the opposite of being on the way the Lord watches over. Which is to say that without the Lord watching over someone/something there is destruction. And so, the godly are dependent on the Lord.
Source: How to Read the Psalms by Tremper Longman (IVP Academic, 1988), p.102