We speak of the day you decided to stop lying. Try to hold that position, and you will find life becomes more enjoyable. You may fail, but you have made a mission statement, and to the best of your ability this is where you stand. Do not be afraid to say; I do not believe that, or, you might like to consider this. That way you are not pushing someone else’s cart. Let them push their cart up the hill.
You can start a conversation by saying; on the 27th of July 2016 I decided to stop lying about that subject. This will open up a new range of interesting discussion, for you can be reasonably sure your discussion partner has not made a commitment like that. They will ask why. You can tell of your reservations, and conflict does not enter into it.
I recommend you start moving toward an answer, because it is a light to see where you are going. It is not comfortable to stay in the dark, but a lie is darkness, so move away from that. Remain open and you will learn, for they will make their best case, and that is what you want. You may have never encountered a person who comes back with a good question before. Most offer ridicule and astonishment that you have not come to the same conclusion they have, and it gets awkward. Not unmanageable just argumentative.