Don't reserve your best behavior for special occasions

"Don't reserve your best behavior for special occasions. You
can't have two sets of manners, two social codes -- one for
those you admire and want to impress, another for those whom
you consider unimportant. You must be the same to all people."

-- Lillian Eichler Watson

Nobody can be you as efficiently as you can

"Do not be awestruck by other people and try to copy them.
Nobody can be you as efficiently as you can."

-- Norman Vincent Peale

It is amazing what you can accomplish

"It is amazing what you can accomplish if you do not care who
gets the credit."

-- Harry S. Truman

Remember there's no such thing as a small act of kindness

"Remember there's no such thing as a small act of kindness.
Every act creates a ripple with no logical end."

-- Scott Adams

Challenge is a dragon with a gift in its mouth

"Challenge is a dragon with a gift in its mouth... Tame the
dragon and the gift is yours."

-- Noela Evans

Mistakes are a part of being human

"Mistakes are a part of being human. Appreciate your mistakes
for what they are: precious life lessons that can only be
learned the hard way. Unless it's a fatal mistake, which, at
least, others can learn from."

-- Al Franken

Mistake are not errors but lesson to be acquired. Let us not be afraid of committing mistakes, because it is only by having mistakes that we grow and develop. 

Politeness and consideration for others

"Politeness and consideration for others is like investing
pennies and getting dollars back."

-- Thomas Sowell

We can never tell how far and wide the fruit and effect of our politeness and consideration will be, just keep on doing it because somehow we can help many people and inspire others.

Although there may be nothing new under the sun

"Although there may be nothing new under the sun, what is old
is new to us and so rich and astonishing that we never tire of
it. If we do tire of it, if we lose our curiosity, we have
lost something of infinite value, because to a high degree it
is curiosity that gives meaning and savour to life."

-- Robertson Davies

Anything that we haven't see and encounter yet are new to us, although they are already existing long time ago. But the nice thing is that, anything that are new to us gives new experience and delight. The experience of happiness can't be bought by any amount, we will only appreciate it because it's priceless.