This verse describes the first two items of a list of five things that might make the Israelites forget about Yahweh (verse 11): "when you eat and are full" and "when you build good houses."
Here "heart" represents the inner person. To become prideful and no longer obey Yahweh is spoken of as if the person's heart is lifted up. Alternate translation: "you will become prideful and no longer obey Yahweh" (See: [[rc://en/ta/man/translate/figs-metonymy]] and [[rc://en/ta/man/translate/figs-metaphor]])