According to the Arizal, one should recite before Shacharis, “I accept upon myself the mitzvah to love my friend as myself.”

A child asked his father, “I would understand reaffirming one’s love for Hashem before prayer, but what is the connection between loving other Jews and prayer?”

The father smiled, “That’s a question that makes sense from your vantage point,” he told his child, “but one day, when you’ll be married and have a family, you’ll understand. Parents are so happy when their children come to them and say, ‘I love you,’ but that happiness is secondary to the joy they feel when they see that their children love each other. That’s what makes a parent’s heart sing. He wants to hear that we love every single brother and sister.”

~ R’ Yitzchak Dovid Grossman