Avoid frequent eye strain, for the long-term health of your eyes. While the occasional squinting isn't going to do much harm, if you're doing it on a daily basis, your vision could be in danger. Experts recommend getting an exam to determine if your strain is due to needing glasses and to otherwise go easy on your eyes.
People who wear contacts need to take particularly good care of their eyes. While contacts are very useful for vision, if the materials are not properly cleaned and maintained, it can be potentially damaging to eyes. Make sure your contacts are the right prescription and that you follow all instructions provided by your health care professional.