Ecclesiastes 7:19 says, Wisdom strengtheneth the wise more than ten mighty men which are in the city.  I believe Solomon was warning us against relying on worldly strength, or power, to make us secure.  We deal with sinful people in all situations, as Matthew Henry points out.  Even the best of people are but sinners, either redeemed or unredeemed.  We cannot find peace and security in this world, no matter how strong or how many strong people we have guarding us.  It is only in wisdom, the acknowledgement that God is ultimately in charge no matter what happens on this earth that we can find peace.  Evil will continue to work to destroy even the most powerful person or nation, but we as followers of Christ must put our faith in Him.  This means, I believe, that we must seek His guidance in all things and not rely on our own intelligence. No matter how brilliant we may be, if we don't look to God for guidance, we are acting the same as a fool.  Verse twenty says, For there is not a just man upon earth, that doeth good, and sinneth not.  We may feel that we are pretty good people and really don't need forgiveness, but Solomon reminds us that there is none without sin.  If we could redeem ourselves, then Jesus would not have needed to die on the cross.  Verse twenty one says, Also take no heed unto all words that are spoken; lest thou hear thy servant curse thee.  We don't need to wonder about everything people say about us.  If it is the truth, it will either cause us to be prideful if it is good, or bring us despair or anger if it is a lie.  We really cannot control what people say about us, so the best action is to simply live under God's leadership and forgiveness.  Even if we were to hear our servants, or those we in a position of power over, curse us, we are not to become angry and self-righteous.  Solomon gives us a good reason for this in verse twenty two, which says, For oftentimes also thine own heart knoweth that thou thyself likewise hast cursed others.  If we are followers of Christ, we always need to remember that we are simply sinners saved by Grace.  We may not have even cursed anyone, or shown anger toward anyone, openly, but we are held to a higher standard of what is in the heart.  We cannot become angry at sinners for sinning, because we ourselves are sinners.  We must hate the sin, but forgive the sinner.