There are reasons, you see: The life of Petunia Dursley.

[Spoilers to OOTP] After the Order of the Phoenix, Remus Lupin dreams about his best friend.

In which Draco Malfoy stops breathing, Crabbe and Goyle wonder, and Harry Potter sings in the shower.

War. And more war. And Harry/Draco/Severus.

Draco and Ron. A brief, little interlude. What does Ron do when he's lost his Harry, or Draco his Snape?

The fourth and last of the 'Lessons Trilogy', Severus and Harry have their first fight. At long last, the series is finished. There will be others in the Universe, however, there are still several dozen loose ends to tie up.

Sequal to 'Lessons in Reputation and Job Hunting', an add-on to the end, in which there are Public Displays of Affection and the love potion is discarded. A surreal relationship takles reality.

Sequal to Lessons in Language and Manner; Severus finds Harry a job. A surreal relationship gets stranger.

In the middle of a brutal war, two wizards meet. Again.

A surreal conversation after the war. Two people find each other. Severus Snape/Harry Potter

Snape watches Harry.

Pure, unadulturated fluff. Domestic Bliss, Pre-existing Relationship. Harry Potter/Severus Snape

Late at night when the lights go out, Draco fears and Harry soothes. A pre-existing relationship. DM/HP