Honesty is the best policy.  Why is this? 
Because a part of you always knows truth, is truth, has no opposites, is
only Love.  That is spirit.  There is another part of you that feels it
must protect itself, make itself look better in some way, or come out
ahead.  This is ego.  This is the part that cares not about truth,
but about separation.  This is the part
of you that fears.

Why do you want to speak anything but truth?  It is a good question to ask anytime anything
less than truth is upon your tongue. 
Acknowledge ego and tell it to go away. 
Bring love to the forefront, and with it, honesty.