Know thyself and other adages

I have written many times about the practical and moral basis for telling the truth.  The basis is full of, well, practical features of being truthful compared to lying.  But there is an element of lying that seems important to survival, and this element concerns one of the most basic reasons for truthfulness, namely self knowledge.  From Hamlet comes the quote

“This above all: to thine own self be true
And it must follow, as the night the day
Thou canst not then be false to any man/Farewell, my blessing season this in thee!”

The reasoning provides a virtuous pattern, provided one accepts that lying and deceit are morally abhorrent behavior.  Being false could come purposefully to ones benefit, but it could also lead to misguided actions such that ultimately, undesired outcomes are produced simply because of self deceit.

The problem with all of this is that change often requires, well, a change of heart.  What is true today about oneself may not be true tomorrow.  With the change of heart, is there admission of being false in the past?  Or perhaps the better sentiment to the Hamlet quote is

This above all: to strive to be true to thine own self.

Here we acknowledge the challenge of knowing oneself.  Socrates preceded Shakespeare with 'Know thyself.'  But there is more.

“The only true wisdom is in knowing you know nothing.”
"To find yourself, think for yourself."
"Be kind, for everyone you meet is fighting a hard battle."