What do standing out in the cold rain, a pile of homework, and an emotional breakdown all have in common? They're enervating: in other words, they completely drain you of physical and emotional energy.
A little different from similar words like debilitating or enfeebling, which primarily suggest physical fatigue; the wonderful enervating implies all that plus the terrible erosion of your soul. Not surprisingly, enervate is derived from the Latin enervatus, meaning "to weaken."