Everyone has lied and been lied to. Let it sink in....
It is a fact of life, even when the lies were not intended to hurt you they can. Sparing someone's feelings with a lie means that you have to remember the lie that you told. It could go on for an eternity to ensure they are going to be fine without ever finding out.
What happens when they find out?
In all reality it depends on the person. There are those forgive even the biggest of lies easily while others use the tiniest of lies to shut people out. It is often seen as the ultimate betrayal. It falls under "you can do anything, just don't lie to me," and it's a concept that some people have difficulty understanding.
The mentality is that nothing is as bad as you think it is as long as you are honest about it. There are those that will never understand this concept. They believe that whatever they do is fine as long as they do not get caught.
Liars always get caught eventually. It is in the nature of the deception. You have to rely on your memory of actual and made up events not to get confused. It is why liars never win in reality. It is obvious to some that lying gets you nowhere but not everyone is so insightful.