Passage
For the Lord will not cast off for ever;
For the Lord will not cast off for ever;
Lamentations 3:29 he putteth his mouth in the dust, if so be there may be hope;
Lamentations 3:30 he giveth his cheek to him that smiteth him; he is filled full with reproach.
Lamentations 3:31 For the Lord will not cast off for ever;
Lamentations 3:32 but if he have caused grief, he will have compassion according to the multitude of his loving-kindnesses:
Lamentations 3:33 for he doth not willingly afflict or grieve the children of men.
The verse centers on "lord", "cast", and "ever". It is saying that the verse draws attention to "lord" and "cast", so its meaning should be read from those terms before moving to application.
The nearby context moves from verse 30's "he giveth his cheek to him that..." into verse 32's "but if he have caused grief he...", so "lord" and "cast" belong inside that flow. In Lamentations context, the local focus is covenant, worship, and faithfulness.
A plain takeaway is to answer the verse's own emphasis on "lord" and "cast" with trust shaped by these words, not by a vague optimism outside the passage.