I am incapable of lying to myself, which is why I will always tell the Truth. But socially it is impossible to always tell the Whole Truth to others, so we must be selective with how much Truth we tell. I never tell outright fabrications, but if a sin of omission is still a sin, then I will have to lie every day of my life because the truth is too difficult for most people to live with.
If someone asks me for the Whole Truth, I will give it to them freely no matter the circumstances. To do otherwise is unacceptable.