Praise the Lord because He is good and because His Name is pleasant. Usually when the psalmist calls to praise he gives a reason. First, because He is good: this should go without saying, but it still needs to be said; this should never be doubted, but at certain times it needs to reaffirmed strongly over against the negative feelings of real life. If God is good (and He always is), then life is good (so praise Him).
Second, His Name is pleasant: the name of God is the Presence of God. If the Lord is present then everything is pleasant, that is, gracious joy and pleasing peace fills the room. There’s a sweet, sweet spirit in this place (so praise Him).
The two specific reasons for praise are creation of nature and the creation of Israel. Both creations are a result of prevailing over enemies: the empty darkness and the chaotic deep, and the gods (demons) of Egypt, Pharaoh, Og, Sihon, and of the Canaanites. Then He could give the Land to the People = promise fulfilled.
The triangulation of the Lord, the Promised Land, and the Covenant People comes together at a point. That point is the Cross where God, Kingdom and Church meet. So at the “crossing” praise Him.