Expression of regret

when we regret
for any cause
we want to go back
to past and make it pause

we think oh lord
what i have done
how can i make it up
but i cannot run

i have to face it
face it
for good
if only a word
that i can put

to express
that we are in grief
and regret for
the reason in brief

a word that can end
a word that is always same
one and only expression of regret
sorry