The Zohar [Bereishis 48(b)] teaches that the mitzva of lighting Shabbos candles should be performed specifically by the wife. The Zohar explains that at the moment that the wife lights Shabbos candles she resembles Hashem who illuminates “the candles” - i.e., the neshamos of His children.
The Zohar then teaches that due to the great honor of resembling הקב“ה in such way, the woman needs to light Shabbos candles with a joyous heart. And through the performance of this mitzva, adds the Zohar, the woman receives a great merit to raise righteous children, and on top of that, she causes her husband to be blessed with a long life! The Zohar concludes with the following line: “Therefore, she needs to be careful in this.” It appears, that line is telling a woman to be careful to always light Shabbos candles with great joy, because those great blessings in her home (righteous children and longevity for the husband) are dependent on the joy that she has at the time that she lights Shabbos candles.
