Accept love of every Jew before davening

The Arizal taught that before beginning Shacharis one should take upon oneself the mitzvah of "love your fellow as yourself" and intend to love every Jew like his own soul. Through this, one's tefillah is joined with the prayers of all Israel and can rise and bear fruit. This instruction is printed in many siddurim at the start of davening: "Hareini mekabel alai..."