...to thine own self be true,The standard take on this bad Dad's advice is that this lying gasbag mouths platitudes that he himself does not follow. We usually regard "to thine own self be true" as one of those man-in-the-mirror, listen-to-your-conscience schemes.
And it must follow, as the night the day,
Thou canst not then be false to any man. Polonius, in William Shakespeare's Hamlet Act I
More recently, there has been a more narcissistic interpretation, along the lines of Follow Your Bliss, Do As You Please, Hold On To Your Dreams, Who Gives A F*** What Anyone Else Thinks. We should be grateful for the change, because the exaggeration points up the flaws in the original idea. Our "selfs" are formed in the context of others. We really have no self except in a social context. As we mature and gain control of the something that is us, we internalise the others, choosing among them, and orienting our behavior to the best of them, even when they are not present. This is, I suppose, a self of a sort, which is able to choose what others will be its context: who we will live up to.
Being true to one's "self," then, is to ignore the context of the impact we have on others. It is ultimately a selfishness. The truth is closer to "To others be true, and it must follow, as the night the day, that thou will be true to thine own best self."