Answer: the saying simply signify doing things the wrong way.
Explanation: the saying "dont put the cart before the horse" is an idiom which means things should be done in the right order. A cart is a wooden device which traditionally comes behind and dragged after a horse. So putting the cart in front of the horse could end badly.
It has been commonly said that there is a time for everything under the sun and trying to take shortcuts or override due process could be very dangerous.
To put the cart before the horse could be as useless as it is dangerous. For example, buying a saddle without a horse. A saddle is used for riding a horse and it would be completely useless to have a saddle unless you have a horse.
Answer: It means that people show their true colors when there by theirself and they arnt typically fake around other people but only they know their true selves its just like the expression "What you do in the dark always comes to light"