You Kant Do That on Television

Kant begins this section by describing how in order for us to morally judge our actions, we must will our maxims into universal laws in order to ground them as those in pure reason. However, when it is the case that we do actions that inherently contradictory, we are not willing our maxims into false universal laws (which according to Kant is impossible) or even believing the opposites of our maxims to be true. Instead, our inclinations force us to view the categorical imperative twice, once with pure will and again with a will tainted by our inclinations. This allows us to transform the universal law into generality. In turn, we use this generality to make exceptions for ourselves (but just this one time, I swear.) and perform the contradictory action.
This can be seen when one considers those who refer to themselves as “social smokers.” When they do not smoke on their own, they are following what appears to be a universal law of not smoking. However when placed in a social situation where others are smoking, their inclination towards smoking allows them to say “I’m at a party/bar/whatever; it’s ok to make this exception.”
This is also one of Kant’s ways of proving the necessity of a priori principles. Because we view our actions with the taint of inclination afterwards, we must use a priori ideas to judge our actions because that can be done without inclination regardless of whether the action actually happens.
Kant also goes on to speak about how in our actions, we must never treat people as purely a means. We instead must regard each rational creature involved as an end in of themselves. This is done by having any other rational party be completely in agreement and in understanding of what they are doing, how they are helping you, and what your goal is. Thus it becomes duty to keep up your fair share of the bargain whatever it may be.
Thus when borrowing money, if you attempt to do so without any intent to return said money and lie to the person you are attempting to borrow money from, you are in error, for this is treating someone as simply a means. But if you borrow money with full intent to repay and make it clear that you will, you are respecting the will of the other rational being involved and therefore treating them as an end in of themselves and not just a mean.