When you tell the truth, you feel better with yourself and with God. You feel that you are a better person and you don't feel guilty.
People will trust you if have a good reputation of honesty. Success is always associated with trust.
3. Good Health
You don't have to remember anything. People who always tell the truth have less concerns and stress, not having to make up stories and keeping up with them. Therefore they live a healthier life with a peaceful mind.
4. Good Relationship
This is also associated with number 1 reason, no matter if this relationship is personal or professional, telling the truth removes that double out of the way and improves the relationship.
Walk your talk, because we all know that the truth will eventually come out and the lie will be out there in the open.