According to the poem "Faces" by Sara Teasdale, what is it that people try to hide from one another?

In many ways, Teasdale's poem talks about the masks that
people wear in order to conceal their own sense of self from
others.  The insight that come across in Teasdale's poem is one of a masquerade, where
people don different masks in order to fully conceal their pain and their own
sense of shame and embarrassment that lies at the heart of their being.  The
speaker, presumably Teasdale, is arguing that the modern construction of progress and
social conformity is one where there is a sense hiding and concealment in
consciousness.  This permeates in how people relate to one
another:

Do
you know how much you tell

In the meeting of our
eyes

How ashamed I am, and
sad

To have pierced your poor
disguise?

In this stanza, the
"disguise" can conceal one's own sense of shame, guilt, doubt, and insecurity that the
speaker feels is hidden underneath the "city's broken roar." This hidden reality is what
keeps individuals sustaining through the rigors of daily life.  Yet, the speaker does
not exclude herself from this condition, as the last line reflects that the "meeting" of
eyes between the speaker and the other people is a reflection that they see through her
mask and she sees through theirs.  In this, there is a realization that a hidden reality
is how all reality operates.  Teasdale once wrote that she was "a flower amid the
toiling world."  Perhaps, it is this condition that is being hidden behind this element
of "disguise."