Always tend to the Big Three: plentiful sleep, daily vigorous exercise, good nutrition.
Get your GTD game right — Read Getting Things Done once a year. (https://itunes.apple.com/us/book/getting-things-done/id357926889?mt=11)
Practice Pomodoro — Unless circumstances do not permit, pomodoro through your GTD widgets. 25 minutes on; 5 minutes off. Repeat. I like this Mac app: Tomatoes (http://www.dollaropath.com/tomatoes/). (see also: http://pomodorotechnique.com)
Use Timeboxing — Context switching is evil but unavoidable. Clump types of context switching (many/frequent vs. few/infrequent) via timeboxing. For example, I use 7AM - 10AM for few/infrequent (eg. concentration-heavy project work (low cotext-switching)) and 10AM to 5PM+ for many/frequent (eg. meetings, email (high context-switching)).
Adhere to Inbox Zero — A bloated inbox is death. Get it to zero at least twice a day and O.H.I.O. (Good video: https://www.youtube.com/watch?v=z9UjeTMb3Yk)
Via GTD, Pomodoro Technique, and Timeboxing (see above), be fully present with exactly one task at a time.
Become an expert regarding self locus of control vs. other locus of control — Putting energy where Other controls and You do not causes suffering. Here is an ASCII venn diagram: ( you ( shared ) other ) Never conjoin your well-being with anything outside your control.
Reframe anxious, obsessive ruminations as How Questions. Contrived example: if you’re obsessively ruminating on the thought “I’m doing a bad job” reframe it as “How can I do a better job?” Your brain will happily chew on the How question and yield positive results without toxicity.
(Almost) every time you walk somewhere, do walking meditation. Be present in the each moment with your breath and steps. Do not cling to or push away thoughts as they arise. Similar spot-meditations can be done while opening doors, washing hands, etc.
Debug your “thought source code” to prevent runtime thinking errors — Cognitive distortions lead to suffering. Learn CBT techniques and practice them as needed. (Feeling Good by David Burns, MD. — https://itunes.apple.com/us/book/feeling-good/id572757284?mt=11)
Minimal caffeine (or none). Minimal alcohol (or none).
Practice "shit cricket" — Dispatch small (less than 2 minutes to complete) items immediately as they appear.