Búyào fā píqì.
不要发脾气。
Keep your temper under control.
Notes:
不要(búyào): don't
发脾气(fā píqì): to lose one's temper
Example:
A:不要发脾气。
Búyào fā píqì.
Keep your temper under control.
B:滚!
Gǔn!
Get out!