Conjecture: When most people talk about "controlling their emotions", they are constructing a narrative to explain the fact that their emotions happened to subside long enough for them to experience something that feels from the inside like making a decision to calm down.

At least in my case, 'controlling my emotions' is an indirect process that mostly involves controlling my attention and modifying my behavior and environment: Intentionally taking a break from thinking about the distressing thing until I've calmed down; doing things that are distracting, like watching a movie, or calming, like taking a nice shower; and arranging my environment to provide calming stimuli, like relaxing background music.

The specific procedures that work best seem to vary substantially from person to person, but procedures of this general type do appear to work for at least a significant fraction of people. (You do have avoid the failure mode of not going back to deal with the problem once you're calm for best results though.)

(Most situations where I have had people encourage me to think selfishly have ended in rather terrifying displays of sadistic cruelty on my part, because that's simply the only model of 'selfishness' that my brain can really wrap its head around.)

I am reasonably confident that I can help with this via IM, by being a role model if nothing else.