A piece of cake
A task or activity that is easy to complete
Get the green light
To get permission to do something
Let the cat out of the bag
A secret that was supposed to be kept quiet that was told
To cut someone some slack
To not manage someone very strictly, to not be critical
A couch potato
A lazy person who watches too much television
Once in a blue moon
Very rarely
Kill two birds with one stone
To solve two problems with one action
To be hard on someone
To criticize or to manage someone very strictly
That is the way the cookie crumbles
That is just how it is
To pass with flying colours
To pass something with a high score
Back against the wall
Forced to do something that you would rather not
Get something out of someone's system
To do something you really have been wanting to do
Have bigger fish to fry
Have more important things to do
The grass is greener on the other side
People think that they will be happier if things were different
Doing something you don't want to do, but also expressing that you're making a proactive sacrificial choice
Burn bridges
To do something, or anger someone, to the point where you cannot go back to how things were
Two peas in a pod
Nearly identical, very similar
A golden opportunity
A very good chance to achieve something
To skip steps, or not do things completely
Leave out in the cold
To be ignored or not considered