Love is or it ain't. Thin love ain't love at all.
Morrison refuses the idea that love can be handed out in careful portions. For her, love is not a dial you set to a comfortable level. It either takes hold of you or it is something lesser wearing love's name. The line is spoken by Sethe in Beloved, a formerly enslaved mother answering the charge that her love for her children is too thick. Her life was shaped by a system that treated the people she loved as property, so for her, holding back was not prudence but a kind of surrender. The line reflects Morrison's wider concern with how slavery bent and endangered love. The novel doesn't simply endorse Sethe, though, since her fierce devotion has terrible consequences, so the words are both a defense and a question.
Today, you might apply this by looking honestly at where your affection is hedged. Maybe you only reach out to a struggling friend when it is convenient, or you send a quick message when what they need is an hour of your attention. The point is not to love recklessly, but truthfully. Either show up properly, with a phone call, a visit, or a difficult conversation, or admit that what you are offering is something smaller than love.