I suggest tackling this from a psychosomatic perspective. The body is an indirect but very powerful agent of change to the mind, Give yourself the permission to be calm and collected and deserve an average, wonderful, American middle-class day without guilt or anxiety. Enjoy that yummy sandwich and coffee and count your blessings. Avoid breathing like a bull in a fight. Avoid walking fast as if you're in a Jason Bourne movie. Avoid thinking rapidly, as if you're a hacker in a bad Hollywood movie. Real-life badasses are often deliberately slow. Real-life geniuses are very slow at the beginning when you ask them a puzzle. Secret : Expand the gap between perception and deliberate-thought as much as possible. That's where the magic happens.
Thus, using your body, allow your mind to reach a place of inner calm. Turns out that Clarity is the perfect path to doing anything good or great. Because it naturally leads to slow-thought, which leads to natural Know Thyself questions, which lead to self-confidence and a moment-by-moment ability to discriminate between what I want to do right now to be genuinely happy vs. what you should do right now as an employee, as a boyfriend, or other role-player (external conditioning). This leads to exercise, cutting down work hours to focus on a startup business plan, being a good serial killer, or whatever it is that you realize as part of the everyday slow Know Thyself process.
All the best! I'm sure you'll do quite well based on what you wrote!
tl;dr version : Deliberately Slow => Mental Clarity. Rest = automatic, by natural design.