Studying for next week's sermon on the end of Proverbs 14 & beginning of ch. 15, it strikes me how blatantly unspiritual some of Proverbs is (stick with me for a minute). There's all sorts of talk about having a good reputation (22:1), getting and keeping significant portions of money (13:22), not getting people mad at you (15:1), and so on. I often find myself tempted to look for deeper, more theological, more Christocentric truths...but God's point in 15:1 is: if you don't run your mouth, people won't be mad at you, and this is a good thing.
The question remains: Why is there so much down-to-earth stuff in Proverbs, so many pieces of advice that would fit perfectly into almost any worldview/religion? Well, that point is the point. God is passionate that, through the wisdom of Proverbs, the way His children live open doors for ministry and the gospel. So He wants us to be nice and not get people mad at us (15:1); why? Yes, because He cares for our well-being; but also because His plan was always for His people to shine forth the truth of the gospel in every mundane and "non-spiritual" part of life. The most average, normal parts of our lives, if directed by Christ, have the potential to become places where people are cared for, where others see that Christ makes little, everyday differences.
[Note: I don't really believe anything is unspiritual. In fact, the whole book of Proverbs is a great reason to reject the idea that something can be unspiritual, unaffected by a relationship - or lack thereof - with Christ.]