There’s no area of your life that’s separate from the others. Your health will impact your work. Your work will impact your relationships. Your relationships will impact your happiness. Your happiness will impact your performance. It’s an interconnected system. And if one of the systems is out whack, the others are inevitably impacted by it. The investment with highest ROI is the one you make in yourself, and the way you get that ROI is by making the following five essential investments.