In the introduction of the book of James, the writer starts by identifying himself as James as well as stating the purpose of the book to "the twelve tribes scattered among the nations" (1:1). Following this brief introduction, the writer proceeds to emphasize the necessity of trials and temptations. These, according the James, produce perseverance (v. 3). This verse then leads into verse 4 that speaks of growing in perseverance.
The NIV translates verse 4 to say, "Perseverance must finish its work so that you may be mature and complete, not lacking anything." This verse seems to describe the importance of growth. Growth that must reach a point of perfection. The Greek word for "perfect" is teleion which is used twice in this verse. Both times the NIV translates this word as "finish" and "mature."
This word, teleion, speaks of the Wesleyan idea of sanctification. Sanctification is a process that also happens in an instant, or what John Wesley called a "crisis point." According to Wesley, sanctification was a continued process in life. Even when we are sanctified by God's grace, we continue to grow. As we apply this aspect of sanctification to this verse, we can see that Wesley agrees with what James writes about.
Sanctification is about growing and persevering through the tough times of life by living obediently to God's Word. This growth sooner or later reaches a point where we are made "mature and complete." However, it does not end there. Our work continues on as we continue to "not to be lacking in anything" (v.4).
James later goes on to mention about finding wisdom. Wisdom is what we are to seek as we seek a relationship with the Lord to be with.