But I point out in Hebrew that there are two different words for "bless"...So you have barak which means "to bless", and then you have this word ashrei.
The word barak means "to be filled with the potency for life". It's the ability to reproduce. So that when God blessed the creation, it was to be fruitful and multiply. Now when you carry that over to the NT, Jesus blessed the disciples. He himself never married. He's not saying to them be fruitful and multiply physically, but be fruitful and multiply spiritually. It's a different form of the kingdom. So that's the word "to bless", barak.
Now the other "to bless" is ashrei. The word used here [in Psalm 1:1]. And that word ashrei means that you have a blessed destiny. It usually refers to the future. And that future, that blessed future, is based upon your present relationship with God. The blessed person when you use ashrei may be in deep trouble at the time...This is a quote from Eliphaz in the book of Job. This would be the Greek equivalent of ashrei - makarios. He says "Blessed is the one whom God corrects". We don't think a person who is being disciplined is particularly blessed, but that's a blessed person. "Blessed is the one whom God corrects, so do not despise the discipline of the Almighty, for he wounds, but he also binds up; he injures, but his hands also heal" [Job 5:17-18]. You have a blessed future. So be thankful that you're a blessed person because God is disciplining you to give you the celestial city. You see how that's different from the word "fill you with potency with life and victory"? It's a different word.
Or another illustration is from the Greek of the Beatitudes of Jesus. Who are the blessed? It's not the way we normally think of it. "Blessed - makarioi, plural - are those who mourn, for they will be comforted...Blessed are those who are persecuted because of righteousness, for theirs is the kingdom of God. Blessed are you when people insult you, persecute you, and falsely say all kinds of evil against you...Rejoice and be glad, because great is your reward in heaven..." (Mt 5:4, 10-12). So the blessed person is a person who has this great reward in the future. That is not translated by "happy". It's totally inadequate for that. I agree the average person doesn't understand it always, but I think it carries more than just being happy.
Professor Bruce K. Waltke, What Do "Person" And "Blessed" Mean In Psalm 1?