As obsession brings extreme emotion, and it all quickly fades once you have attained what your heart desires. Being obsessed with making someone love you leaves you feeling empty once that person finally does love you. Convincing someone to love you to the point of becoming obsessed will leave you feeling hollow once you succeed.
The thrill, the intense emotion, the constant thoughts and worry running through your mind, it all quiets down, leaving you feeling empty. You tricked yourself into believing that those thoughts you had and those emotions you experienced were love. You tricked yourself into believing that what you felt was love and love alone.