You can just slap a resistor in series, which will induce a drop in potential over it. That, in turn, will mean the potential difference across the capacitor is

You can just slap a resistor in series, which will induce a drop in potential over it. That, in turn, will mean the potential difference across the capacitor is lower, leading to a more shallow exponential decay of the current over the circuit - ie a slower discharge. And that's just a passive circuit, with an active circuit you have a lot more options. Note: I studied maths and computing so I could very well be wrong. I would appreciate being set straight by elec eng majors!