In the general thought of congregations that I've attended, "The valley of the shadow of death" means this passing world, as does "The great tribulation." A sober or even gloomy assessment of this world is not limited to the ancient world; far from it. Some modern publications seem to revel in talk of doom, blame, and fear. And so it is well that we interrupt this scheduled programming for an important announcement: God keeps his promises. And he loves us, frightened little kittens* as he might see us. We're frightened because we know that human solutions will eventually fail us (see: estate planning, and insurance).
The days are surely coming, says the LORD, when I will fulfill the promise I made to the house of Israel and the house of Judah. In those days and at that time I will cause a righteous Branch to spring up for David; and he shall execute justice and righteousness in the land. In those days Judah will be saved and Jerusalem will live in safety. And this is the name by which it will be called: "The LORD is our righteousness." (Jeremiah 33:14-16)Those who believe in the promises made by the God of Israel dare to hope: not in our own names but in the Lord's. It allows us to let go of the fear, to breathe more deeply, and to look forward to the days to come.
* Hatchlings would be more scriptural, with the gathering chicks beneath the wings, but I find kittens more relatable if you'll pardon the license.