Not only is this man "blessed" but he is wise, his wisdom leads to his blessing. He walks not; stands not; and sits not in the evil way.
Note the progression, walking, then standing, then sitting. Sin always leads in a downward path, and it will bring us to a standstill in our lives. We quit growing when we indulge in sin, and, if not lose ground, we don't gain anything toward God or growth in Him. Our life becomes stagnant. Anything that becomes stagnant is subject to corruption; it is the life, and growth that keeps us going. An illustration would be stagnant water, it turns green and begins to smell very rank after a time. It is not good for much of anything, definitely not for the purpose which it was given.
Especially in counsel we need to be wise. Too many seek counsel in the wrong places. Bad counsel will cause us to stand in the way of sinners, and sit in the seat of the scornful. Seek only Godly counsel, for what have we to do with the ungodly? Experience is not always the wisest counselor, many men have experienced much, and can give great swelling words of testimony, but their counsel is ungodly, and therefore unprofitable.
"But his delight" ought to be in nothing but the "law of the Lord." It takes time to "delight" in the Word of God, but diligence will lead us to delight. The way to diligence is to "meditate" in it "day and night." You cannot help but grow fond of something that is on your mind constantly, and is a matter of prayer, especially when you know it is good. There is a special blessing to all who do so. Keeping our minds on Christ is a command in the scripture, and a great benefit to us. (See Col. 3:1)
There is an old saying that "familiarity breeds contempt" but not so with the Word of God! Familiarity breeds love, the exact opposite of contempt! The more we become familiar with the Word of God, the better it seems to get. The better we get.