The psalmist, in 119:73 knows that God’s hands have “firmed him up” — the way the sun is “fixed” in the sky at midday, the way pillars hold up the building, and the way a king has been established on his throne. Why does the psalmist care that God’s hands have firmed him — established him?
Because it is the Lord who established him, the Lord can give him understanding to learn the mitzvot, commandments. The connection is important: What the Lord makes is made for a purpose.
The Lord has made us, has established us, has given us a constitution, to know him and to love him and to honor him and to obey him. A six iron golf club is established to act like a six iron; using it as a putter is a misuse and it doesn’t do what is designed to do on that green. A car is established to drive on roads; using it on a railroad track or in a river does not permit it to bring out its designs. A knife is established to cut; using it as a screwdriver bends its tip.
The Lord has fashioned us to to know and do his will. This is what we were made to do. Humans are at their best when doing what they were designed to do.