@Khethil,
that's a quote I have found out, not through the quote, but myself. I have seen that when I am not happy with myself, I can never be happy for someone else. (I understand I am exchanging the word love for happy, but excuse my switch, you can use them interchangeably if it helps) I am always skeptic, negative and pessimistic; never wholehearted and genuine in any of my compliments, though logically, what they are doing is praiseworthy in my opinion. There is always something lingering in the back of my mind that prevents me from being in the moment. Shame is what it is in my case. I am ashamed of who I am, and what I do not do. Partly because I have high standards for myself, and partly because I cannot do the simplest task I set out to do. But I do not do what I think I can, and should do, and thus this is the source of me not being fully happy with myself.
I can kind of relate to hawkeye's notion, but not as in-depth nor well understood as him. I have just recently isolated this notion after years and years of this feeling going on, I never had the cognitive capacity to understand my situation (mainly through denial and lack of self-reflection). Maturity, unbearable feelings of disgust and depression, and actually being proud of myself for once allowed me to identify this feeling and origin of shame.
So I don't think this is pragmatic nor empirical for you, it is just my opinion and experience, but if I don't love myself, it is impossible for me to fully love someone else. I'll perhaps come up with a more rigid, well constructed argument when I am more aware and familiar with this feeling and notion.
Until then, I think hawkeye said it best. and I also agree with his notion on marriage, very insightful and educational to me, and perhaps also for those that are in the middle of a long relationship.