Let us now visit one of Jesus's most explicit teachings:
"Teacher, which commandment in the law is the greatest?"
He said to him, "You shall love the Lord, your God, with all your heart, with all your soul, and with all your mind. This is the greatest and the first commandment. The second is like it: You shall love your neighbor as yourself.
Love defined
We take St. Thomas Aquinas's defnition of love: to love is to will the good of the other as other. That is, to love is to want what is good for another person, and not for your gain but for theirs.
What love isn't
This definition is critical, because along with it come several important points:
Love is not wanting what's easy for another person. Instead, love demands what's best for them.
Love is not blindly accepting another person, nor is love tolerating another person. Instead, love demands bringing a person from a worse state to a better state.
Love is not (simply) feelings toward another person. Certainly feelings have their place in love, but on their own are not sufficient to be love. Instead (or more accurately: "additionally"), love demands action to bring about another person's good. That is, love is not passive; it requires willingness to act. To will the good of the other.
Love is not selfish. It is not use. It does not seek one's own good. Instead, love demands the good of another person for their own sake.