Economics, in its most simple form, follows the Conservation of Mass as defined in physics. Basically, everything goes according to plan so long as outflow is less than or equal to inflow. Failing that, the balance is upset and things start getting complicated. Before long, the calculus starts revolving around “imaginary numbers” (like eleven-teen and thirty-twelve) and people making statements like “less is more”.
Similarly, the problem with having a line of credit on The V-Bank is that when you go on a spending spree, your bike will occasionally need to lay down for a rest.