/diy/ - Do It Yourself

Kinda weird question, asking here because I don't know how to phrase it for Google:

I made a simple flasher circuit with a PUT and a capacitor, so when the capacitor voltage exceeds a set threshold it lights up the LED until the voltage goes below it. I'm wondering why the capacitor goes a little above the threshold voltage instead of instantly starting to discharge, and conversely, why it discharges more than just barely below the threshold voltage when lighting the LED. Is there a simple answer to this, or is this one of the trial-and-error things where it kinda arbitrarily works out that way? Thanks.