Falling down; feeling down

Nights are fast drawing in
Too early the sun says goodnight
As it disappears then so do I
For I feed, I feed on the light.

To sweeten the pill comes the fall
The reds and yellows and brown
But in turn then an end to it all
As leaves all come tumbling down.

Shorter days, longer nights take their toll
Midwinter days barely start
Light has retreated by four
As depression enwraps my whole heart.

Stalwartly, I must resist
The glory of Spring must remember
Take a deep breath, keep my head
All change come the end of December!