The two most powerful tools you possess are the words yes and no. Please use them wisely.
However, there's a more important power than those positive and negative reinforcements. It's called fiduciary, and it's not what you say to someone after they sneeze, although it is a sort of cleansing term. It means that you stand up for what's "right," as in what's financially responsible, and it's crucial to your loan-granting process.
At the end of the day you—Oh fair money lender—are on the front lines of risk management for a bank and for the financial system. The financial institutions are counting on you to approve loans that'll get paid back (and make them a profit) and to deny anyone who'll take the money and run off to hide in a bunker somewhere (that they paid for with the loan you gave them).
It's a power and responsibility balance, and one that matters a lot. When the screening process is broken and too many bad loans get made, we see scary economic upheavals like recessions and depressions.
Having this kind of power over our economy, even if it's only a little portion of that economy, is a huge responsibility, so please don't just go throwing money around.