To put the cart before the horse : It is an idiomatic expression. It means to stop somebody to do something or hindrance somebody's work.
The horse pulls the cart, hence it is placed before the cart to enable it to pull the cart. On the contrary, if one puts the cart before the horse, the horse will not be able to draw the cart. Therefore, by placing the cart before the horse, you are creating a block for the horse.
For example: My cousin never allows me to prosper. Last week, I thought of viewing a movie, but he put the cart before the horse stating that the movie has earned bad reviews and advised me not to waste my time and money on it.
Some people are pessimists. They always try to put the cart before the horse, when people talk positive.
I have worked hard on this project and going to present it tomorrow. I hope my team members don't put the cart before the horse before I present it.