To pull the rug out from under someone means to withdraw support or take away help or assistance that is essential to something or someone. The impression this idiom gives is that by pulling the rug out from someone, they risk falling or being toppled without the support that was once there. 

1. My tax bill really pulled the rug out from under me. I don't know how I'm going to be able to pay it.
2. Our eviction notice really came as a surprise. I felt like someone pulled the rug out from under my family and I.

1. I've decided not to jump ship. My boss has always been good to me, so I just couldn't pull the rug out from under her like that.
2. If I quit my job to follow my dream, I risk pulling the rug out from under my own feet.