Negan has severe anxiety, and he's 70% positive he has depression. Rick just wants to help him.
The all-out war with Negan may be over, but there is one battle Rick still has to face. The battle within himself. With Carl dead, Mischonne not by his side, Rick is spiraling out of control. So when Rick and Judith go missing in the blizzard, it's up to Negan to find them. Once he finds the nearly frozen two, he looks after Rick and Judith and it brings the two men together.