The theme of Parshat Ki Tavo is the importance of remaining in a state of Simcha, or joy. We see this in connection with the Bikurim, first fruits. And we see this at the end of the rebuke.
After listing all of the curses that will come to the Jewish people, if they do not observe the Mitzvot, the subject of joy is mentioned. Some explain that the reason for all of the curses is because, “You did not observe Hashem with joy, when you were given everything.”
It is clear that it takes work that we call, עבודת נפש, workings of the soul, in order stay happy. There are two basic ingredients necessary in order to get to this goal. The two points are related. First, one must realize how dangerous it is to be jealous of others. Being obsessed with another person all of the time, does not allow a person to focus on his own blessings.
This leads to the second point. We must never stop counting our blessings. We must focus on what we have, rather than what we don’t have. We must simply learn to be happy with our lot in life. No jealousy, and being content with all that we have, will help greatly in our quest to remain in a state of joy.