By "do so little for you" it really means someone who doesn't meet emotional needs you have deep down inside, reciprocate your love or service, or let you know you are deeply cared for - NOT by our society's means either (i.e. material things) but doing it in the way YOU genuinely respond to.... I have love to give regardless of my well being....Period
But you can learn to forgive and move forward, and extend grace. BUT you can NEVER EVER move forward until you have moved through the pain. Wherever you heard that, they were telling you a lie from satan. Why? Because that lie sprang forth from the father of lies and they both need to be told STOP, read God's Word. Then tell satan to go back to Hell. "Resist the devil and he will flee from you."