This poem by Paul Laurence Dunbar (~1898) expresses it SO well:

We Wear the Mask

WE wear the mask that grins and lies,
It hides our cheeks and shades our eyes,—
This debt we pay to human guile;
With torn and bleeding hearts we smile,
And mouth with myriad subtleties.

Why should the world be over-wise,
In counting all our tears and sighs?
Nay, let them only see us, while
          We wear the mask.

We smile, but, O great Christ, our cries
To thee from tortured souls arise.
We sing, but oh the clay is vile
Beneath our feet, and long the mile;

But let the world dream otherwise,
          We wear the mask!