Brachos 4:2-3

Brachos 4:2

Rabbi Nechunya ben Hakana had special prayers that he recited upon entering and leaving the beis medrash (study hall). His colleagues asked what they were. He replied, “On entering, I pray that I should create no problem by erring in halacha. On leaving, I give thanks to God for my assigned portion.”

Brachos 4:3

Rabban Gamliel says that everyone must recite 18 benedictions (Shemoneh Esrei) daily; Rabbi Yehoshua says that one must recite the themes found in the 18 benedictions (i.e., an abbreviated version). Rabbi Akiva says that if one is proficient, he recites the entire Shemoneh Esrei, otherwise he recites the abbreviated version. (Things are different nowadays, since we have printed siddurim. In the time of the Mishna, prayers generally had to be committed to memory.)