Curiosity outlasts motivation. Motivation needs a reason. Curiosity just needs a question.

Motivation runs on justification, so it dies whenever the reason weakens: the test is over, the season ended, nobody is watching. Curiosity needs much less, only something you genuinely want to know, which means it keeps working on the days you cannot be bothered. One of the two is a mood and the other is closer to an appetite. Appetites come back on their own.

Rather than trying to feel motivated about a subject, write down one real question about it you would like answered. Go after the question instead of the chapter. It will still be interesting on Thursday.