Selling your soul

 If you've sold your soul, it means you're willing to do something bad to gain money, power, or success. 

If you say that someone sells their soul, you mean that they do something immoral or bad in order to get something they want such as success or money. 

To compromise our core values to get something might be selling our souls. If we have a good soul and values for our lifes we might find only paths to little compromise and sell our souls to get something.