These are the contexts of the quotes tweeted from @sueannbowling between November 28 and December 4, 2013. All but the last are from Songsmith, by Andre Norton and A. C. Crispin.
“You will need all the belief you can summon.” Alon is suggesting that his magic – which he understands – and Eydryth’s songsmithing – which she does not – may be able to let them build a bridge over the final illusion.
“Her power is stolen. Mayhap her knowledge is lacking.” Eydryth to Alon, speaking of Yachne.
“Fair can be foul.” What Eydryth remembers Sylva telling her: not to trust outward appearance.
“You must. There is naught else to be done.” Alon, arguing to Eydryth that she must take Monso and ride to find her kin, while he goes after Yachne.
“A promise, once having been spoken, must be kept, regardless of cost.” Part of the song Eydryth sings her father while waiting to see if Dahaun’s mud will cure him
“Hope is something we will need sorely in the coming years.” Eydryth’s reflection on the meaning of the name, Trevon, just given her youngest brother.
“I’m glad the lesson sank in.” Tourist Trap, by Sue Ann Bowling. Penny’s response to Roi’s insistence that he is wearing his warnoff after a previous problem.