Faith and Need for constant Inspiration

 Rav Yakov asks why didn't the Jews accept Moshe's  Message from G-d that they would be freed from Egtpt? He notes that initially they had believed in Moshe but now they ignored him?

Shemos (6:9) But when Moses told this to the Israelites, they would not listen to Moses, their spirits crushed by cruel bondage.

וַיְדַבֵּ֥ר מֹשֶׁ֛ה כֵּ֖ן אֶל־בְּנֵ֣י יִשְׂרָאֵ֑ל וְלֹ֤א שָֽׁמְעוּ֙ אֶל־מֹשֶׁ֔ה מִקֹּ֣צֶר ר֔וּחַ וּמֵעֲבֹדָ֖ה קָשָֽׁה׃

He answers that the Jews maintained their faith by reading the book of Job and other works on Shabbos

However after the first meeting with Moshe, Pharoh made them work on Shabbos so they no longer had the inspiration they had before and this is what is meant by short spirited