"To thine own self be true, and it must follow, as the night the day, thou canst not then be false to any man."
-- William Shakespeare - Hamlet
This quote from Hamlet has been expressed by hundreds of great thinkers for hundreds of years. If you genuinely believe that what you are doing is the right thing to do, that you are connected to your most important life values and virtues, nothing else matters. You will be in peace.
That does not mean that you have certainty that what you are doing is right and what others are doing is wrong. However, you have trust in yourself, in your ability to act on behalf of your highest self.
I have a little game when I have a challenging decision to make. It is called my board of directors.
I will role play with these fictitious characters, take their advice, and after careful consultation, I will take action.
I am the COO - the Chief of Operations Officer in that game. I'm not the big boss, the CEO, who has the final say on these decisions. I work to serve the CEO, the Chief Executive Officer. That guy is me, as my optimum self—me as the best version of myself, at my full potential. I know I cannot be that guy, but I also know that I can consult with that guy and try my best to serve and obey him.
Then, I have all different kinds of directors for different purposes. I have a chief literary officer to whom I "present" my writing; I have a philosophy unit of directors. Usually, they are Seneca, Marcus Aurelius and Epictetus, etc.
I try not to invent words that would come out of their mouths. I have studied these people, and I have tons of notes in my knowledge management system software. I can ask: what would they do or think, and research keywords that associate that mentor with a particular subject.
Pretty cool, heh? You don't have to go into such complexities, though.
To keep it simple, instal a dialogue between you, the COO and the best version of you the CEO.
Whatever you do next, you know you did the best you could and that you trust your CEO to have helped you in the direction that is true to you. That trust must be nurtured in a way that it is unshakeable. Sure, you will make mistakes and take wrong decisions, but that was not because you were acting as a vicious part of yourself, but because you are human and humans make mistakes. The core intention was made according to the values and beliefs that are important, both to you and to YOU.
And so, if you are true to yourself, as our friend Billy said, you will be true to all the people you interact with. That trust you create will turn into a very powerful (and beautiful) boundary between the opinion you have of yourself and the opinions others have of you.
This magical wall will protect you and help you find and keep peace.
The only truth we will ever find is the truth that we seek.