like a sitting duck

Source

There is a need to admit to oneself that sadness is swirling within.  It is a kind of sadness brought about by circumstances beyond one's control. A defenselessness-induced kind of sadness. There is no issue about other faculties--one is still able to function efficiently. It is those brief quiet moments in between accomplished tasks when unfortunate realities pour down like a sudden thunderstorm of moroseness. The kind that you do not want to spread around like a self-righteous pharisee parading one's fast by deliberately looking haggard so as to obtain the pitiful approval of people. But a comforting clutch from a loved one truly helps. Kind words from more empathetic persons too. Once again, the important point is to allow oneself to immerse in the emotion like a warm bath that later becomes lukewarm and eventually dissipates---evaporates. As opposed to forcibly removing a drain plug in an attempt to be immediately rid of the emotion. 

As a conclusion, here is Pablo Neruda's "Ode to Sadness" as an example of the irrationality of a typical woeful state: 

Sadness, scarab

with seven crippled feet,

spiderweb egg,

scramble-brained rat,

bitch's skeleton:

No entry here.

Don't come in.

Go away.

Go back

south with your umbrella,

go back

north with your serpent's teeth.

A poet lives here.

No sadness may

cross this threshold.

Through these windows

comes the breath of the world,

fresh red roses,

flags embroidered with

the victories of the people.

No.

No entry.

Flap

your bat's wings,

I will trample the feathers

that fall from your mantle,

I will sweep the bits and pieces

of your carcass to

the four corners of the wind,

I will wring your neck,

I will stitch your eyelids shut,

I will sew your shroud,

sadness, and bury your rodent bones

beneath the springtime of an apple tree.