The problem with [many common] notions of prayer is that we cannot have an intimate relationship with someone to whom we cannot speak honestly–that is, someone to whom we cannot show our ugly side, or those large clay feet of ours. We in this culture are all psychologically astute enough to know that honest, unguarded speaking is essential to the health of family life or close friendship. But do we realize that the same thing applies to our relationship with God? That is what the Psalms are about: speaking our mind honestly and fully before God. The Psalms are a kind of First Amendment for the faithful. They guarantee us complete freedom of speech before God, and then (something no secular constitution would ever do) they give us a detailed model of how to exercise that freedom, even up to its dangerous limits, to the very brink of rebellion.
-Ellen F. Davis, “Improving our Aim: Praying the Psalms,” Getting Involved with God, pp. 8-9
A Thinking Reed 
“We in this culture are all psychologically astute enough to know that honest, unguarded speaking is essential to the health of family life or close friendship.”
If this is the case, then the vast majority of families and friends are unhealthy. It is completely unrealistic to think or expect that humans – who lie all the time whenever the truth will make them suffer – should be expected to speak in unguardedly or honestly. Now, that doesn’t mean they lie ALL the time, but this doesn’t specify a percentage and implies that you have to be honest all the time or your relationships are all going to be unhealthy. That’s quite obviously complete BS as there are huge numbers of people (probably the majority) who lie in their relationships and yet are still functions. And I don’t necessarily mean lies about infidelity, you could be lying about how you like dinner, how someone looks, where you’d like to go, how you feel right now, etc…
Show me someone who claims never to lie and I’ll show you a liar.
I don’t think anybody’s suggesting that people are (or even necessarily should be) completely 100 percent honest all the time. The point, I think, is that a certain level of honesty is indeed essential to meaningful family relationships and friendships. If you can’t speak your mind to your spouse, freinds, and loved ones and share with them the really important things, then relationships are bound to remain at a pretty shallow level. And Davis thinks this applies to our relationship with God too.
So there are people out there who are lying to God? That seems… like maybe they don’t understand the definition of omniscient? But maybe I’m not understanding you because I’m not – omniscient that is. Maybe what he really means is not to lie to yourself. Lying to God, mainly due to the whole omniscient thing, seems really really pointless.
I think the idea is that even though God knows everything that is knowable (including the contents of our minds presumably), it’s still important for the relationship that we be honest with God. By analogy, there’s a significant difference between confessing an infidelity to your spouse and him or her finding out about it from some other source.
Call me wind because I am abotulsely blown away.