Lyric discussion by AGreenMan 

Cover art for Head Up High lyrics by Black Rebel Motorcycle Club

Someone close to the author is leaving because they feel no one listens to them and they're afraid they wont make it far unless they just leave and say they're through. They feel that nothing stays the same, and even remedies (drugs?) are just forced happiness.

But the author makes it clear that "this song is not about you, but the life that stands without you, your body and blood, you're leaving us all" (so maybe we can infer that he's singing about a relative or close friend, and that they're leaving everyone who loves them).

The singer has to hold his head up high to deal with what they're going through (these true sensations)

My Interpretation