You Are Normal Too shows the story of Derpy overcoming past heartache to find happiness in the present. Her relationship with her first lover is told in bits and pieces, but this goes into far greater detail about them coming together, breaking apart, and her life afterward.

Reading this first can give greater insight on the mental struggles Derpy goes through in the story, but this story is told in an abridged form in chapter 2 of You Are Normal Too, so there's no spoilers for the main story.

Link to the main story.
http://www.fimfiction.net/story/230048/you-are-normal-too