"I think Dumbledore might have hoped I would be able to exercise some control over my best friends. I need scarcely say that I failed dismally." - Remus Lupin
"Yeah, well, you made us feel ashamed of ourselves sometimes... that was something..." - Sirius Black
Temperance encourages calmness and moderation, as well as self-control. It calls for seeking a balance between extremes in order to better achieve enlightenment.
Mild, thoughtful Lupin is indeed frequently a calming influence to all those around him, a rare treasure among the wizarding world's hot-tempered personalities. This sensibility perhaps comes from his tragic circumstance early in life - having to "temper" down his werewolf nature in order to fit into society. Unfortunate though his condition is, it gave Remus his quality of introspective levelheadedness.