The closing 22nd stanza of Psalm 119 repeats many of the themes of the previous 21 and summarizes this epic to the majesty of the Word of God.
Seven passages contain prayer for "understanding," which depends on the gracious ministry of the Holy Spirit in our hearts and minds (John 14:26). Our finite minds cannot understand God's eternal truths apart from revelation and the "mind of Christ" granted at salvation (1 Corinthians 2:16).
Thirteen passages use "according to thy word." Nothing that we can do pleases God more than our efforts to "magnify" His Word in our lives and ministries (Psalm 138:2). Every sentient creature will be judged by what is "written in the books, according to their works" (Revelation 20:12).
Eight stanzas include the prayer to have God "teach." Again, apart from the Holy Spirit in our "new creature" (2 Corinthians 5:17), we would be empty of both understanding and wisdom. Through reading and meditating on God's Word, after salvation, we grow effective and gain maturity.
The writer also promised in eight stanzas to "not forget." Our minds need to become stabilized with memorized Scripture and our hearts ready and sanctified with the stored Word of God so that we can "give an answer" both to those who ask us (1 Peter 3:15) and when we need guidance for our own life decisions (Colossians 1:10).
The psalm ends with a prayer for all: "Let thine hand help me; for I have chosen thy precepts. I have longed for thy salvation, O Lord; and thy law is my delight. Let my soul live, and it shall praise thee; and let thy judgments help me. I have gone astray like a lost sheep; seek thy servant; for I do not forget thy commandments" (Psalm 119:173-176). HMM III http://www.icr.org/articles/type/6/