Feelings of a Window Pane

Some days the sun spills in,
Through the window pane,
And everyone feels its warmth,
And happiness,
While on other days,
It is dark and raining,
Everyone feels the dankness,
But this is what I am,
A window pane,
Easily looked through,
Some days I can put a curtain down,
To hide what is happening on the inside,
Then nobody will know,
Is it raining or shining today?