We must remember that boasting about our plans is not only ignorant (since we really don't know what will happen), but it is also evil and improper for servants of God! If you are a Christian, then remember that you live to serve the Most High God (cf. I Cor. 6:19,20)! Humbly submit your will to His in all things.
James' conclusion to this topic comes in 4:17 - "Therefore, to him who knows to do good and does not do it, to him it is sin." This powerful verse, in context, teaches us to live for the Lord today! It is wise to plan in harmony with God's will, but don't neglect the good that can be done now. Don't procrastinate because your life is like a vapor!
In general, James 4:17 also provides an even fuller understanding of what constitutes sin. Yes, sin is the transgression of God's law (I John 3:4), and it is committing that from which God has commanded us to abstain. However, sin is also failing to do what we should be doing! A general problem for many Christians is that they assume they are good because of all the things they don't do. They don't lie. They don't steal. They don't swear. They don't commit adultery, etc. But, simply avoiding evil things is not good enough! We must also do that which is commanded. Goodness is a positive quality; it isn't just the absence of that which is bad. The fig tree in Matthew 21:19 didn't have any bad fruit on it, but it also didn't have any good fruit either! Similar comments could be made concerning the one-talent man of Matthew 25. He was labeled a wicked and lazy servant because of his inactivity; he failed to do the good that he could!
I'm afraid there are many so-called Christians today whose lives are displeasing to God. It's not that they are actively engaging in immoral activity; they are simply not doing the good things that they could in service to Him! Their service for His kingdom is often limited to warming a spot on a pew a couple hours a week. Such a servant is also aptly described as wicked and lazy!
Friends, what about you? Are you so enslaved to your schedule that you don't have time for God and His good works? God rewards those who diligently seek Him (Heb. 11:6). He will take care of those who seek first His kingdom (Matt. 6:33). Are you of that class of people or have you been putting off doing certain things the Lord expects of you--certain good things that you know you should be doing? Are you among the many who deceive themselves by saying: "I'll have more time to study, pray, and share my faith later"? "To him who knows to do good and does not do it, to him it is sin." If there are things you can and should be doing, then do them! Let's get busy for the Lord today! Excuses may get us by in this life, but they won't get the job done come Judgment Day.
Let us summarize the latter half of James 4 before closing. We should avoid all faultfinding and critical judgments. We must not attempt to use the powers and privileges that only belong to God Himself. God must be considered in all of our plans and purposes. We should live for God today by doing those things that He would have us to do because we have no assurance that tomorrow will come.