One area that is often overlooked in attempts to become a more efficient cyclist is in the use of the muscles other than those that are used to actually propel the bike. Any unnecessary, or nonproductive muscle tension or motion consumes energy (that includes flipping off motorists). If you can learn to keep your hands, arms, and shoulders loose and relaxed then you will reduce their energy consumption, and you’ll reduce the likelihood of developing aches and pains in your neck, shoulders, arms, and hands.
Practice relaxing your grip on the handlebars, keeping your elbows slightly bent, and your shoulders dropped and relaxed and you’ll be on your way to becoming more efficient and more comfortable. You’ll probably have to keep reminding yourself to do this for a while before it becomes a habit. I suggest a “post it” sticker on your handlebars that says, “just relax”.