This is addressed to Rachel, weeping for children who are, in that moment, actually gone — exiled, absent. God doesn't tell her the grief was excessive or misplaced. He tells her to restrain it because of something specific that's coming: return. The command to stop weeping isn't “get over it” — it's “what you're weeping over is going to be reversed.” The restraint is warranted by hope, not by minimizing the loss. Worth noticing, too: “there is hope for your future” is spoken into a present that, from the inside, likely felt hopeless. The hope wasn't visible yet when the promise was given — it had to be taken on the strength of God's word alone, before the children actually returned.