I’m a long-term meditation and yoga practitioner and teacher, was told I have textbook ADHD but as it turns out, that diagnosis, which is probably true to some extent, is overshadowed by a recent diagnosis of narcolepsy. – similar symtoms, similar treatment.
There are quite a number of different practices and techniques in meditation, different schools of practice, different schools of Buddhist thought, etc. I myself have practiced zen for many years, as well as mindfulness (Jon Kabat-Zinn) and Tibetan practices.
One of the basic (and also more advanced) practices is to focus attention on the breath. In Tibetan Buddhist practice, this is called shamatha (sham-at-a). The purpose is to develop stability in attention by focusing on a specific object (or mantra, for example) and the “goal” is to develop the ability to maintain this focus for longer and longer periods of time. It’s taught as a beginner’s practice but it is also a very advanced practice. It’s very portable since the breath is always with us, no special equipment required 
Another is the mindfulness practices that LSA is referring to. It’s different than shamatha, but also good practice. It can be easily carried over into everyday life by trying to be mindful of little events, for example, walking meditation can be a mindfulness practice where you are mindful of every little movement as you lift and move your foot. Or, as Thich Nhat Hanh suggests, stopping when the phone rings and taking a few breaths and being mindful before you answer it.
There are also much more advanced practices like zen koan practice or complex visualization practices. Practice can be endless.
One of the hazards of practice is wanting to stay in that calm, quiet place. That’s not how life is! Life is messy, complicated, sometimes wonderful, sometimes awful. So what can be very useful is to be comfortable with all of the emotional and physical and mental experiences of your life. Meditation can help provide space for you to embrace all of that, and, as LSA says, perhaps make a different choice than you might have if you were more reactive.
Getting back to ADHD issues (and in my case, narcolepsy) – meditation was not enough. I require meds in order to be alert and aware. But now that my health issue is stabilized, I feel that I can work more deeply on meditative practices. It’s like driving through a blinding snowstorm, you can barely see, and it’s all you can do to stay alert and on the road (pre-meds). Now I am out of the snowstorm, not that there won’t be more turbulent weather, but I’m in a much better position to navigate my life. And I’m looking forward to diving more deeply into practice.
So good for you! Keep working.
I hope that’s helpful.
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