It's a relief when he lets go and begins to cry, because she knows that he's hurting so badly, and keeping it all inside will cause him so much more pain that just letting go, allowing himself to truly feel. She holds onto him tightly, rocking a little, gently rubbing his back. "It's okay," she whispers, turning her head to press a kiss into his hair. "I've got you. You're safe."

Joan has her own pain, of course, but she can't show it now. Perhaps later, when Ted is feeling better. Or perhaps she'll cry at 221B, with Sherlock awkwardly standing guard and stiffly patting her back. Whatever she does later, she needs to be strong now.