I came up with that quote during a discussion with a friend regarding selflessness. A black hole is an empty void that pulls in all light and all that enters it (planets, stars, etc), and nothing can escape from it. Now imagine continually making sacrifices for someone to the point that you lose yourself. Never be so selfless that you become a self less (or less than yourself). Now imagine that this person is apathetic and shows little appreciation for the sacrifices made. I explained to my friend that there's a point where you have to stop and realize that as sweet and thoughtful as it may be to harbor that level of consideration for anyone, there are some people who simply take it for granted and people who, quite frankly, don't deserve it.
When you make a sacrifice, you're not doing so with the hope that the other person will kiss your feet and shower you with praise, but you'll just have to be careful of who you choose to be selfless with. It's a terrible sensation to constantly give to someone who is selfish, to someone who sucks out all (correction, who pulls out) the light in you, leaving you feeling empty and insubstantial. At some point, you'll realize that your sacrifices have all been in vain.
So, like I said, there's no sense in giving to a black hole.