why we say lies?

I think there are so many reasons to say a lie:

* we think that is better hide something to the person you love, you think is better lie to them, that made them cry.
* Sometimes is better lie, because if you talk or tell your problems or your feelings, you feel weak, and you don't want to your friend has pity to you.
* Is better to lie to avoid a problem.

But even if you hurt someone is better to say the truth, because if you lie, you have to lie again and again, and you didn't see the pain that you're doing to that person.