The first key is deep restful time out. We're a full-on society now. Highly interrupt driven. Very little down time. We rarely stand nor sit doing absolutely nothing. Is that a problem? Only when you notice the power of the alternative: have a dedicated part of the day where for 10 minutes or so you do nothing: no phone, computer, book, paper, conversation, food, drink........ just be. Try it. First few times you'll probably feel annoyed with 'wasting time'. But then the benefits of clarity, fresh thinking and proportion will evolve.
TBC.