Take what you're given, follow on the road back down. Not even Heaven knows.
Annotation
The meaning of this lyric is rather opaque. However, it seems to suggest that our lives are a matter of fate and that this fate is something we must follow, and the following of our fate is inevitable, but the wildness, the specialness, and perhaps even paradoxically, the vacantness of our life, exceeds all logical bounds, hence the lyric "not even know heaven knows" which juxtaposed against the other part of the lyrics seems to suggest that even though that our lives on the surface seems rather straightforward, the complexity moving them forward is beyond anything we could ever imagine.