"Easy does it!"
Meaning: Be very careful! / Don't do anything too fast or too hard!
Example:
Tom: I'm going to use a rotary buffer to polish the paint of my car.
Jerry: Easy does it! If you move the buffer too fast, you might burn the paint.
Last week's idioms:
yes-man
zilch
all right
be a piece of cake
can't make heads or tails of (something)