Unrequited love

The pain that lingers the longest when you love someone deeply but she doesn't love you in return isn't the loneliness or sense of loss you experience when you think about her; it's the certainty that she will never understand the depth of your affection, that you will never be able to show her how much you love her. That love has nowhere to go, no release, so it just stays inside, hurts like hell, and she'll never know and, worse, never care.