To speak the truth is to say things exactly as they are. You will need to be able to see clearly to say things exactly as they are. It's OK to say what you know or see without calling it truth.
There are people who deliberately lie or are habitual liars.
You are right, there are people who are familiar with lie they don't even see it as something bad anymore they lie with every opportunity they see, this set of people started this kind of attitude years back and it has entered there DNA so stopping it will be difficult if not impossible, I have a friend that is so familiar with lying he lie in every situation and don't even see it as a big deal, Because of his lying attitude I don't trust him again and known of his family members believes anything he says anymore even when he says the truth they think his lying and that has really affected his life but still he just can't stop lying.
Lying causes a lot of things damage to us and it can even cause us to lose important things in our life for example if you are known to be a lier no body will like to do business with you or even trade with you, you may even get sacked from your job and because of your constant lying attitude even when you are in a big problem and you call for help no body will take it serious because everyone will believe you are lying, being honest is very important in our life it help us become successful every one will want to do business with you or trade with you, honestly will make a lot of people to trust you.
Lying will bring you more harm than good.