Sometimes the anger goes out without ever coming to the surface. Sometimes, like a wildfire, it rages aboveground until it's quenched, but continues burning slowly, underground and out of sight.
If I've been made furious on an issue, and then I stop raging after a while, I've still got my anger until I say otherwise. It isn't in front of me. It isn't occupying much, if any, of my time. But it's still a hot coal in my belly, only blazing up when fuel is tossed on. Sometimes fuel that's tossed isn't flammable enough to set the anger to blaze again, just stir it a little and send up sparks, but the next time someone tosses in some gasoline, there will be plenty of other things to keep it burning after the first flare dies...
Sometimes the anger goes out after a time, and I find with surprise and appreciation that I'm not angry anymore.
Until I say I'm not angry about something, though, odds are I still am. I just won't mention it, not unless it breaks out again. Nothing's happened to make me that angry again -- I'm just angry still.