Start each day with a plan.  Plot out and prioritize your work.  Be realistic and build in time for interruptions.
 

Schedule physical exercise throughout the day.  Take a 5-10 minute walk every couple of hours.
 

If you are unclear about what you are being tasked to do, ask for clarification.  How can you relax when you don't know if you're working on the right things?
 

Chunk your work into manageable sized pieces.  Looking at an entire project can be daunting.  Once you break the work down, schedule time to do each piece.
 

Know your body rhythms and honor them.  If you're a morning person who wakes with energy, schedule your most complex work early in the day.  If your energy drops mid-afternoon, that's a great time to do rote work like answering emails.
 

Strike a healthy work/life balance.  Do what you like and your energy will follow. Enjoying yourself makes you more effective in each area of your life.
 

Keep healthy snacks within reach.  Almonds in your top drawer, celery in your fridge, lots of bottles of purified water.
 

Stay Curious.  Try doing things differently.  Exercise your creativity and grow your comfort zone.  Ask the question, "how else can I do this?"
 

Anticipate obstacles and make a strategy to work around them.
 

Make a list of champions.  These are people who believe in you.  Keep their phone numbers handy and call when you need a lift.
 

Accept 'good enough'.  Not all work has to be A+.  Determine which tasks just need doing.
 

Laugh loud and often.