The notion is that one is believed to be lying regarding something they refuse is true -- or in other words "lying to themselves" really means telling yourself something that isn't true when you know it is.
My questioning is, can you not know a conclusive fact about something, and still be lying about it to yourself unknowingly? Indirectly? Here's an example if this doesn't make enough sense:
A woman has been struggling to get in shape after weight loss. She had just run 2 miles a few weeks ago, but today she went outside and felt little motivation and overall didn't run more than half a mile. She doesn't feel like she couldn't have pushed herself -- more so she feels like motivation was missing, so she stopped. She wonders thereafter, "Did I quit by choice or by weakness?"
In short, she tells herself that she stopped running by her own will -- not by the existing possibility that one could be less fit or capable at that time. If she isn't sure if her lack of motivation prevented her or her fitness, and assumes she quit due to not being interested and not a lack of ability, is she lying to herself? Must one be 100% aware of the fact that they are lying to themselves, or is it indeterminate?
Other factors can apparently cloud one's assurance of something in their mind, which can postulate and make you wonder whether or not inconclusive awareness can affect one's ability to cloud truth and mask it in another way -- or whether or not the actual factors have proven first assumptions.
These kinds of questions may be controversial and used as defense in legal/court proceedings.