I actually talked to my T about this phrase 2 weeks ago...
She gave me "Wisdom from the Road Less Travel" by M. Scott Peck to read. In it, it said: "Can't love anyone unless you love yourself". That really upset me.
I told my T, I disagreed. I told her the people I love, I truly do love. She said she believes me. BUT, she also said I do love myself... That was confusing...
She explained that I often do things that shows that I love myself: hygiene, eating well, exercising, comforting myself when I'm upset, reaching out for help when I need it, taking my medication, fighting for things I want, playing with my dogs, even tattooing the place I SI'ed. She's right

In that regard, I do love myself. So I do have the ability to love others.
And two other quotes from the book that actual support my belief that I do truly love:
“Love is not simply giving; it is judicious giving and judicious withholding as well. It is judicious praising and judicious criticizing. It is judicious arguing, struggling, confronting, urging, pushing, and pulling, in addition to comforting”
“Genuine love is volitional rather than emotional. The person who truly loves does so because of a decision to love. This person has made a commitment to be loving whether or not the loving feeling is present. If it is, so much the better; but if it isn’t, the commitment to love, the will to love, still stands and is still exercised”