"Your mind is your instrument. Learn to be its master"
This says so much, and is so difficult to do, but necessary if we're to be the Captain of our ship and not the passenger. I'm sure we all know people who are completely reactive to their uncontrolled negative thoughts and even with advanced age and a lifetime of experience; are still willfully unaware that the only thing they can really control is "their own mind". Someone at this level of awareness can expend lots of energy trying to control people and events around them for their own purposes - like a Seinfeld episode the results usually end up in more stressful, complicated situations with negative consequences (usually for others).
We've all been there I'm sure. Tai Chi practice has been helpful through the practice of "shen" putting your spirit within - listening to/awareness within your body. This attentive listening to your body & mind cultivates relaxation and the calming of your emotions. Along with the process of placing your intention/awareness, learning to yield and let go of the ego, this mindful practice over time develops your will and a moment-to-moment awareness of your emotions, body and thoughts. This sets you on the path to "control your instrument".