差之毫厘，谬以千里
the discrepancy of a single hair will lead to an error of a thousand li
the slightest divergence leads far astray
a small discrepancy leads to a great error
己所不欲，勿施于人
do not do to others that which you do not wish to be done to yourself
师心自用
self-opinionated
师直为壮
an army fighting for a just cause has high morale
师出无名
send army out without a righteous cause
dispatch troops without a just cause
席不暇暖
be constantly on the go
常备不懈
always be on the alert
all-time preparedness against war
平白无故
gratuitously
without any reason
平步青云
spring to heaven from the level - make a sudden rise in life
rapidly go up in the world
平铺直叙
dull expressions
speak or write in a dull, flat style
平分秋色
go share and share alike
go halves
divide equally
go fifty-fifty
平淡无奇
nothing remarkable
nothing exciting
pedestrian
平地风波
unforeseen trouble
a sudden storm on a calm sea
a crisis out of nowhere
平地楼台
high buildings rise from the ground
平地一声雷
a sudden big change
平起平坐
be on an equal footing
平心静气
calmly
平易近人
amiable and easy of approach
年富力强
in one's prime
年高德劭
of venerable age and eminent virtue
年轻力壮
young and vigorous
年深日久
as the years go by
幸灾乐祸
gloat over other's misfortune
be glad when other people are in difficulties
gloatingly
度日如年
one day seems like a year
days wear on like years