Adding to the First Three and the Final Three Blessings
A person should not ask for his needs in the first three blessings or last three blessings of the Shemoneh Esrei. This ruling applies specifically to the needs of an individual; however, regarding the needs of the public it is permitted. (Shulchan Aruch Orach Chaim 112:1)
The above ruling is based on a passage in the Talmud: “Rabbi Chanina said: In the first three blessings the worshiper is likened to a servant who offers praise before his master. In the middle blessings he is like a servant requesting an allotment from his master. In the final three blessings he is like a servant who has received his allotment from his master, expressing thanks and gratitude and then departing. (Berachot 34a) The Mishneh Berurah explains that since the first three blessings were designated for praise it is not appropriate to ask for one’s personal needs when reciting them.
The reason it is permitted to make requests for the needs of the public is because it is actually considered a praise and honor to someone when he is needed by the masses (Olat Tamid; Shulchan Aruch HaRav; Mishneh Berurah). It is for this reason that it is also permitted to say Yaleh v’eyavo in the blessing of Modim, and the requests that are inserted during the High Holidays and Ten Days of Repentance in the first three blessings. (Beit Yosef) The Aruch HaShulchan writes that this is also the reason why the third blessing “You are holy…” is extended to include requests during the High Holidays. (Dirshu)
Though we find requests in the final three blessings similar to the middle blessings, the Avudraham explains that it does not present a problem because they are all requests that primarily give honor to
The Piskei Teshuvot writes that although it seems from Tosefot (Megillah 4) that one could theoretically add a request in his own words in the first and last three blessings as long as it conforms to the above conditions, the custom today is in accordance with the apparent opinion of the poskim (later halachic authorities), to make requests only if they have a set text for everyone, such as “Remember us for life…” and other similar requests.