something that you say when you have decided to behave in a less pleasant way.

I'm fed up with people taking advantage of me. From now on, it's no more Mr Nice Guy.

• play by ear
• play cards close to chest
• play cards close to your chest
• play cards right
• play cat and mouse
• play devil's advocate
• play dirty
• play down
• play down something
• play fast and loose with
• play fast and loose with someone
• play fast and loose with something
• play footsie
• play footsie with
• play footsie with someone
• play for a fool
• play for a sucker
• play for keeps
• play for time
• play games
• play God
• play gooseberry
• play hardball
• play hard to get
• play havoc with