Many Siddurim include in the "Shema Kolenu" section of the weekday Amida prayer two texts which some have the custom of reciting at this point in the service. The first is a Vidui (confession for one’s sins) and prayer for forgiveness, and the second is a prayer for Parnasa (livelihood). These texts were composed by Rav Hida (Rav Haim Yosef David Azulai, 1724-1806), who writes that the Arizal (Rav Yishak Luria, 1534-1572) taught that it is proper to ask for forgiveness and for Parnasa during the recitation of "Shema Kolenu."
The question arises as to whether it is proper to add these prayers each time one recites the weekday Amida. Should these prayers be added only on occasion, or is it worthwhile to recite them as a permanent part of the prayer text?
A number of Aharonim, including the Taz (Rav David Segal, 1586-1667) and the Aruch Ha’shulhan (Rav Yechiel Michel Epstein of Nevarduk, 1829-1908), write (Orah Haim 119) that it is improper to add a text to the Amida on a permanent basis. While it is acceptable to add a personal prayer on occasion in the blessing of "Shema Kolenu," this should not be done permanently, each time one recites the Amida. A permanent text would be disrespectful to the Ansheh Kenesset Ha’gedola (Men of the Great Assembly) who established our liturgy, giving the impression that the text they composed is insufficient. The Aruch Ha’shulhan bemoans the fact that "fools" were publishing Siddurim with additional prayer texts that people were including on a regular basis, which, he feels, is inappropriate.
However, the Kaf Ha’haim (Rav Yaakov Haim Sofer, Baghdad-Jerusalem, 1870-1939) cites (in Orah Haim 119:5) Rav Hida’s comments in his Birkeh Yosef (119:2) disputing the Taz’s ruling. In Rav Hida’s view, it is entirely acceptable to recite an additional prayer in the Amida even on a permanent basis. The Kaf Ha’haim adds that when it comes to the Vidui and prayer for Parnasa composed by Rav Hida, even the Taz would agree that they may be recited regularly, each time one recites the weekday Amida. The Taz opposed permanent prayer texts that ordinary people came up with on their own, personal prayers that one decides to add each and every time he recites the Amida. The prayers composed by Rav Hida, however, are based upon the teachings of the Arizal, who encouraged reciting such prayers during "Shema Kolenu." Such prayers may be added on a regular basis, and, the Kaf Ha’haim concludes, it would in fact be a Misva to do so.
Summary: Many Siddurim contain two prayer texts which many add during the "Shema Kolenu" section of the weekday Amida – a confession and request for forgiveness, and a special prayer for one’s livelihood. It is proper to add these prayers to "Shema Kolenu" each time one recites the weekday Amida.