Jamieson, Fausset and Brown on Jeremiah 45:5

5. seekest thou great things for thyself--Thou art over-fastidious and self-seeking. When My own peculiar people, a "whole" nation (Jr 45:4), and the temple, are being given to ruin, dost thou expect to be exempt from all hardship? Baruch had raised his expectations too high in this world, and this made his distresses harder to be borne. The frowns of the world would not disquiet us if we did not so eagerly covet its smiles. What folly to seek great things for ourselves here, where everything is little, and nothing certain!

all flesh--the whole Jewish nation and even foreign peoples (Jr 25:26).

but thy life ... for a prey--Esteem it enough at such a general crisis that thy life shall be granted thee. Be content with this boon of life which I will rescue from imminent death, even as when all things are given up to plunder, if one escape with aught, he has a something saved as his "prey" (Jr 21:9). It is striking how Jeremiah, who once used such complaining language himself, is enabled now to minister the counsel requisite for Baruch when falling into the same sin (Jr 12:1-5; 15:10-18). This is part of God's design in suffering His servants to be tempted, that their temptations may adapt them for ministering to their fellow servants when tempted.