A little bit sad today.

Not because my paper got rejected multiple times, nor because my research is not moving the way I wanted. These things do not make me sad. They make me feel challenged. When I feel challenged, I begin to pay attention, and make plans, and execute them, until the challenge is removed.

Maybe the saddest thing of life is uncertainty. It is a state in which you do not know the answer to a question, and you do not know what to do to find it out. Worse still, all signs are pointing to the direction you would hate, and yet, nothing you could do to make certain. And you would not allow yourself to give up the last slice of hope. To feel sad is to feel hopelessly incapable.

Talking about being sad, who can be sadder than this fellow:

浣溪沙

李煜

风压轻云贴水飞，乍晴池馆燕争泥。沈郎多病不胜衣。
沙上未闻鸿雁信，竹间时听鹧鸪啼。此情唯有落花知。