"Honesty is the first chapter in the book of wisdom." Thomas Jefferson
Disregarding philosophical theories; truth is often tied with honesty. If you are honest, then you are telling the truth. However, telling the truth is not necessarily being true to oneself. I could be telling the truth about my life and how I am living it, but in the same time who I am is completely different than the person I am reflecting in my daily life. Regardless, telling the truth and being honest is simpler than that. You just need to tell it as it is, without sugar coating and without needing to add plots to make it more interesting to your receiver.
Based on personal experiences, telling or knowing the truth can be harsh and uncomfortable. But, telling a lie, believing it and living it will hurt you more than you can ever imagine. You will feel temporary satisfaction; like you've plotted an awesome movie script, and when your recipients believe your script, you feel a sense of achievement and sometimes contentment. Alas my friend, all these false illusions of happiness and satisfaction is just a mere cover over your self denial. You know you are being dishonest, you know you are wrong but your mind tries to block it out as much as you can because you like the illusion of being in control and the master of your own script.
Most of the times, people around you will know that you are being dishonest. They will play the fool who does not know anything, while deep down they wish if you just come clean and tell them the truth. Those who care, will tell it to your face - as it happened with me, and will tell you that living the truth and being true to who you are is much better than your lies and alternative realities. Those who does not care less, will not tell you anything - will let you go in your path blinded, as if you are on the right path. Then, there are those who are indifferent - that's because they are just stones in your path - they just stop you every now and then but do not harm you nor they do you any good.