I really love Yuki Kajiura's music because most of it helps me relax even when the songs are on the sadder sounding side. I'm distracted from like a "sad" tone, usually, by say, studying. So it's just super pretty music to me when I'm focused on something like that.

I really enjoy her OSTs for Madoka, Tsubasa Reservoir Chronicle, Pandora Hearts, and Sword Art Online particularly, but I tend to listen to the music from the former two series more.