Hemera
The sad feeling in this card reminds me of the Six of Wands. There is the same feeling of looking backwards and being stuck in the past. But in the Six of Wands the girl was looking back at her childhood whereas this Knight could be crying over spilt milk. He is looking at one chalice and at the same time the one in his hand is also spilling to the ground. I get the feeling he is forgetting to count his blessings (the wine he had in his chalice) and therefore that also is spilled.
Another way to look at this comes to mind,too. The red wine is nourishing fertilizing the earth. It is the sacred libation and the creative energy that the Knight gives to Mother Earth. The lovely blue horse looks like he understands that this is more important than some of the duties that are expected of a Knight; rushing fast from one challenge to another or a fancy career somewhere.
Another way to look at this comes to mind,too. The red wine is nourishing fertilizing the earth. It is the sacred libation and the creative energy that the Knight gives to Mother Earth. The lovely blue horse looks like he understands that this is more important than some of the duties that are expected of a Knight; rushing fast from one challenge to another or a fancy career somewhere.