Now, before you jump to a conclusion, I'm not leaving the study! These three verses just give us three examples of foolish things --- things to avoid. I'm not saying you have to jump on your horse and race away, so let's look at all three and see what they mean.
First, a foolish person may have conversation that is not profitable nor edifying. (Eph. 4:29) If that person's words are corrupt, or a bad influence on us, then we need to leave that person's company. We can ask gently and kindly that the person "clean up" their conversation, but if they will not, then sometimes the best witness we can be is to graciously leave their company.
Second, foolish people often deceive themselves. It is important for us to understand our "way" and Solomon means our course in life --- our pathway. It's been said in many hymns and songs that we are travelers, and so we need to avoid distractions like being critical of others, and being busybodies. We should instead observe and avoid obstacles, and stay on our path. Foolish people think they are on the right path, but they deceive themselves, like the man who built his house on sand. Another who deceived himself was the man who gave no gratitude to God for his bumper crop, but congratulated himself on his prosperity and said he'd just build bigger barns.
Lastly, there are foolish people who make light of sin, and who mock Christians for their desire to avoid it. They rush into sin, they laugh about it, and encourage others to be wicked as well. In Isaiah it even says that they "call good evil, and evil good." (Is. 5:20) The second part of the verse says "among the righteous there is favor" and I believe that means favor in two ways: the righteous have favor with God, because they repent and ask Him to forgive --- they have favor with man, because they try not to hurt or offend, and ask forgiveness when they do.
I think it's always good to be positive instead of negative, so personally, I think I'm going to strive to have good conversation, to pay attention to my pathway, and do my best to have favor with God and with the people around me! Whoa --- that's a tall order . . . I'm awfully glad the Holy Spirit is here to help me! How about you?