But one thing is needful: and Mary hath chosen that good part, which shall not be taken away from her. Luke 10:42
Jesus looked at Martha and said, "Mary has chosen the good part, which shall not be taken away from her" (see Luke 10:42). "Good part" is the word agathos. It’s contrasted to another word for "good" in Greek–kalos, which means something is "constitutionally good" or, in other words, made well. But kalos doesn’t necessarily imply any practical usefulness or benefit. It may simply look good. Nothing is wrong with it, but it may not have any practical purpose.
On the other hand, agathos–the word for "good part" that Mary chose–is a word that means "good and profitable; useful; beneficial." It is often translated "good works." The Lord is saying, "If you spend time waiting on Me, seated at My feet, it puts something in you. You will not only look good, but you’ll also be good for something." We often look good, but lack [the Spirit]. We must wait in His presence and allow [our service] to be born of relationship.
Sheets, Dutch. 1996. Intercessory Prayer. Ventura, CA: Regal Books. pg 146