Knowing Me

You know if I'm happy,
or if I'm pretending to be.
You know all this with a single glance,
you know me.

I can't say it's a strength,
more of a downfall.
You may notice things you wish hadn't,
after climbing over that wall.

I'm sorry in advance
for the acting ability I don't possess,
and that I wish I could be better,
this I confess.

Better;
I wish I could be;
But now your greatest weakness
is knowing me.