In order to be irreplaceable one must always be different.
若想无可替代，必须与众不同。
If all your skills or personalities can be easily duplicated, or, said in another way, they are not unique, then you may put yourself in dangerous situation, or somewhat unstable situation.
That is because you can be replaced easily, maybe one day you will lose what you live by, then things will be really wrong.
So, try to become ireplaceable, at least let one of your skills be unique.
Write it on your heart that every day is the best day in the year.
请铭记于心，每一天都是一年中最好的一天。
If you live every day well, then every day is the best day in the year.
If you always waste your time, or idle on useless things, then gradually you will find every day will be a misery.