In a simple explanation, opportunity cost is the loss of potential gain from other alternatives when one alternative is chosen. Choosing to forego an expensive vacation to put a larger down-payment on a car brings a loss of relaxation time, but a benefit in a lower monthly payment. Choosing to work late might curry favor with your boss, but will cost you time with your family. Some of the decisions are simple, but others are more complex because of the long-term impact they will have on us and our circle of influence.
Each of us have to evaluate the opportunity cost of life on a daily basis. There is a value that we place on the decision to follow Christ over the influences of the world around us. Some of those choices will be difficult to make and that is why Christ told us that we would need to die to ourselves. It is an active decision to live a life that is worth far more than the temporary, immediate gratification that we often see in front of us.