Summary: Everyone wants wisdom, but Psalm 1 gives more than just good advice, but vital information that can affect your entire life and beyond. It describes two paths in the life of your mind. Choices matter, which one are you making on a daily basis?
This Psalm reminds me of Romans 12:2 (quickview)  “Do not be conformed to this age, but be transformed by the renewing of your mind, so that you may discern what is the good, pleasing, and perfect will of God.”
To be happy means to have thoughts and make decisions as God would. But often our culture puts tremendous pressure on us, like the forming of a clay mold, to model (or “conform”) us after another image, one that is opposed to thinking and acting like God. Instead, our culture wants us to act in self-interest.
Happy (twice happy, really) here is portrayed as a negative—we are happy when we do not do something. In this case it is to be like the culture.
Verse 1 always reminds me of Lot in Genesis 13 (quickview) . Lot was unhappy working with Abram. Abram said “pick a spot” so Lot used his human eyes (whereas Abram had used his spiritual ears to go where God directed) to go where it looked good. No doubt he had heard how well watered the plain of the Jordan was, so he followed that advice and picked it because a well-watered plain meant material prosperity. Eventually that advice found Lot taking the path towards Sodom where he pitched his tent, and eventually joined the city as a resident, though they mocked God (when the angels came to rescue Lot).
Beginning to just bend an ear to the values of our culture will entice you onto a path that leads to a place where you are surrounded by rebellion against God and eventually you are so infected that the only answer is to pull you out of there.
So where do you get your values and what advice do you take seriously? The road to happiness, true happiness, lies on another path.
The word “delight” is a good translation of the Hebrew. It means not only what you gives you pleasure but your wish and desire. What do you delight in? Jesus said: “Where your treasure is, there will your heart be also.” (Matthew 6:21 (quickview) ). What do you treasure? What do you value? That’s what will lead the decisions you make in life.
In one of the most important verses in Scripture, the key to blessing is delighting in the instruction of God. The King James says it is in the “law of the Lord.” The word literally is Torah, which means “a precept or statute” and by that is meant the books of the Law of Moses. So we are talking here about God’s Word.
Now as we go through the Psalms, and really wherever we find an admonition to read, study, and meditate on God’s Word, we can substitute the word “Jesus” in there. John chapter 1 tells us that Jesus is the Word. Not only are we to delight in Jesus and His Word, but we are to meditate on it. We delight “and” we meditate, or let it soak in. “Day and night” basically means all the time.
If we take the opposition of the first verse—I would suggest that the Psalmist is saying that if you “follow the advice” of God’s Word, if you live your life (ie: walk) in God’s precepts, and if you establish yourself within a relationship to God—you will be blessed.