Psalm 119, the longest chapter in the Bible, is an acrostic poem. Each of the 22 stanza begins with letter of the Hebrew alphabet and the 8 lines of each stanza begin with the same letter of the Hebrew alphabet.
Those who obey God's Word and seek Him with all their hearts are blessed. God's instruction is given to us for our own good. God shows us the right path to follow/the blessed way to live. To be blameless/ undefiled is to walk in faith and obedience to the law of the Lord. This requires action. Be doers of the Word, not just hearers or knowers. Happy/joyful are people who faithfully follow the instructions of the Lord. They don't walk in the way of the world or in their own way. They diligently seek God and seek to glorify Him, not selves. They wholeheartedly devote themselves to the Word of God and to God of the Word. The joyful make God's will, God's Word, God's way the rule/standard of all their actions. In return, they shall be guided, comforted, refreshed, strengthened, and encouraged. Very blessed, indeed!