It amazes Katara that Toph has found her place in the world after the war, her place as an adult, so easily and so well. Toph had had to break out of the confines of her childhood and now she is as confident and powerful as... as Aang, in her own way. Everything from running one of the largest trading empires in the Earth Kingdom to finding a husband and raising children, everything seems to come easily to her.
It is as if the war cleared the ground for Toph. She was able to lay down her roots, and she is flourishing.
Katara finds herself thinking of Suki as her travels take her from shore to shore. Suki was a warrior but now the war is gone. There is something in her gaze, something in the small wrinkles that furrow her brow. Suki is missing something, and it isn't Sokka. Although what they had between them isn't over, it hasn't been strong enough to pull Sokka out of the south pole or Suki out of her home.
Just so, Katara feels like she is drifting. She had been the one holding everything together but now their group has grown apart. Katara isn't in the center anymore. Instead she just goes where Aang goes.
There is work to be done, work she cares about, but there is still something missing, and she wonders if she'll ever find it, if she'll ever live her life so intensely again.