Since the main culprit for eye strain is today's culture is time spent in front of a computer, a TV, a cell phone, or another device with a screen, finding alternatives such as reading a paper book rather than reading on your iPad can be a huge help. Also, to reduce the harmful effects of screen time that cannot be avoided (such as on your computer at work), try positioning the screen lower and using an anti-glare screen to diminish the strain on your eyes. If you are having continued eye strain that is bothering you in your day-to-day life, consult your physician. It is possible that you have a vision problem, or another eye condition, that may be contributing to the discomfort and/or tension you feel. It is always better to be safe rather than sorry, and to see a doctor to ensure that nothing more serious is going on (as well as to obtain appropriate medical treatment if needed).
Limit screen time. See a doctor.