"A truthful witness saves lives, but he who utters lies is treacherous"
The justification for lying is almost always that it will save lives, but usually it is the life of the one lying – not others. The truth is what ultimately will save more lives and not all the clouded dark secrets with secrets covering other secrets. Remember this when you are being tempted to lie to cover over something you did. It will save more people, including yourself, if you tell the truth.
Also if you know that you have to tell the truth, then you will be more prone to do the right thing, knowing that you will be unable to justify the deed with a lie.
Notice the liar is treacherous. The liar is duplicitous. Liars look like they are doing you a favor when they are really doing something to save themselves. This is the true test of lying: Who does this non-truth benefit? If it is the speaker, then it is a lie and to be condemned.