唔知一句英文可以點講...

唔好唔開心 ! =]

Never say die. 勿氣餒灰心。
Never trouble trouble till trouble troubles you. 勿自尋煩惱。
God helps those who help themselves. 天助自助者。
God never shuts one door but he opens another. 天無絕人之路。

never give up
If you don't give up , you muct do you best
CHEER UP
Do your best ! 意即 "做到最好", 較適合鼓勵兒童
Way to go!　意即 "做得好! 加油!"
Kick some/ his butt ! " 意即 "落力啲! 加油!" , "比啲顏色佢哋睇"

Kick some/ his a　! 如上, 但較為粗俗, 傳神

Go get'em　!　 意即 "加油! 比啲顏色佢哋睇"
Try your best
Work hard
to make an extra effort
add oil
do your best,
you think you can, you can
Cheer up
give up
keen on
refuels

don't be scare
be storg ang storger

when there is a will, there is a way!