“Life's not all fun and games.”
Your daughter made some bad grades on her progress report at school. You ask her why, and she complains that her homework is boring. You say this because you're annoyed that she would complain about this.
Life's not all fun and games.
This is a set expression. When someone complains about doing something difficult, boring or unpleasant, you can tell them this:
Life's not all fun and games, you know.
The meaning of the phrase is that you can't have fun all the time; you have to work hard sometimes.
The phrase "fun and games" is used in a few other expressions as well. When they're used together like this, it's usually meant to criticize the idea of people doing things that aren't careful or serious enough. For example, you can say this to some children who are playing too roughly:
It's all fun and games until somebody gets hurt.
You can say this if someone invites you to do something fun but you're busy and stressed out:
I appreciate the offer, but I don't have time for fun and games. I have work to do.
This last example would sound a little rude, though.