Question

"This above all:to thine own self be true" explanation

Answer 1

hey .well this famous quote of shakespeare wants us to believe on the fact that we are what we are.   What this actually means is that people should not ACT like someone else. they should be who they are. A  famous personality once said that "there is one thing that is common in all of us and that is that we are all different"
     You don't have to be an Einstein or Shakespeare to be liked by others. All u have to do is be yourself and follow the right path of truth in life.
         even our parents might say to be like that first rank holder or that artist...... but they are forgetting that just like everyone's fingerprint is unique , even our brain and behavior is different.
                You are only one of your kind living in this world.There is no one like you and there will not be anyone like you. So be true to yourself and first love yourself and never try to be a monkey which copies what the other is doing.
   This doesn't mean that if u r bad then u stay bad. That'll be wrong. Be yourself and live a happy life by following the truth.
          

Answer 2

how many people do you know in your life who pretend to be something that they're not? 

Maybe they're trying to make their parents proud. Maybe they're pretending they're not hurt by something so that no one sees their "weaknesses". 

And maybe they've squashed all their passions, all their life's desires to meet what they think society expects of them. 

These people are not being TRUE to themselves. They're ignoring what they would TRULY want because they fear the fallout should they pursue it. 
But that's not all that the quote is about... 

"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." 

That is the full quote. When people ignore what their heart tells them, they deceive themselves. And because they do not know better, they believe the deceit to be truth... and therefore wind up lying to everyone. 

So if one is true to themselves, it follows (just like night must follow day) that one will not lie to others. 

The line is from Hamlet, a beautiful play.