Like newborn babies, crave pure spiritual milk, so that by it you may grow up in your salvation,
Babies crave milk. They want it moment by moment, and they will take it almost every time you offer it. Milk is on their mind, and it is almost the only thing that is on their mind. They want it when they are bored, they want it when they are sad, they want it when they are lonely, they want it when they are uncomfortable or sick, they want it.
Growing up in your salvation will require more than the simple 15 minute daily devotional. Please don't misunderstand me... I am not being judgmental of our hectic schedules. Though, maybe I should, that is not what I am doing here. To crave spiritual milk like Peter is talking about here is a mindset. This is the person who has God on their mind. This is a person who is thinking about God's word, even when there is no Bible near. This is the person who thinks to themselves, "I need to hear from God today!"