Ted may come across as very open, but he's a private man in many ways. He's extremely friendly and loves sharing anecdotes, but when it comes to anything difficult, he guards himself much more carefully. There are few who actually get to see him vulnerable. But he feels a lot safer with Joan and Sherlock, and he can tell that the two of them make an effort to make him feel that way.

Ted feels much the same as Sherlock - pleased and concerned. Which is exactly why he came to find Sherlock. If she does push herself, he wants to make sure they have a safety net for her.