The answer is no. I'm sure your parents had good intentions when they would tell you this. It's not like they wanted you to stop reading, but in actuality, it didn't pose a real threat to your eyes. Squinting actually enhances your vision. The more light your eyes are exposed to, the wider your pupil grows. If there is low light, your pupil become smaller, but making them smaller actually improves your focus. We squint for a reason. By the way, while squinting is helpful and natural, if you catch yourself doing it too often, it may be a sign you need glasses. Either that or squinting is just a hobby of yours.
We've all been told to sit back from the TV - not because your big head is blocking the screen, but because your eyes are too close. Well it turns out that there is no real evidence that sitting up close to the TV damages your eyes, at least not long term. It's mostly kids that have to be told this, and there's a reason why they tend to do it more than adults: children are better at focusing at close up objects without getting eyestrain than adults. The idea that sitting in front of the TV was bad stemmed from when televisions first became household items and it was discovered that they emitted a lot of radiation. TV's were innovated to emit less radiation, but the "you'll hurt your eyes" myth stuck with each generation. While sitting close to the TV won't cause nearsightedness, it could be a sign of nearsightedness. Sit in front of the TV if you truly wish. You may get a headache, but you won't go blind.
You've probably heard that carrots are essential for vision. Carrots contain a great amount of vitamin A, which is essential to eye nourishment. Yet it turns out that going all Bugs Bunny on a bag of carrots may not necessarily make your eyes that much better, and they definitely won't give you superb night vision. The carrot myth has a possible unexpected origin: the British Royal Army. According the UK Ministry of Food, British World War II pilots were successful at shooting down enemy planes at night because their diets were rich in carrots. The UK Ministry of Food, which no longer exists, used this as propaganda to boost the local carrot economy. The rumor is that the British Royal Army went along with this carrot myth to cover up secret radar technology that they were using, which could've been the real reason for their ace nighttime shooting. Since carrots contain vitamin A, they'll of course do more help than harm for your eyes, but vitamin A can be found in butter, milk, broccoli, eggs, squash, sweet potatoes, spinach, iceberg lettuce, mangoes, peas, apricots, and plenty of other foods. If your diet is typical, you don't have to rely on carrots for your vitamin A. As a side, egg yolk, broccoli, and spinach also contain lutein, which may help prevent the degeneration of macula in the eye.
Ever see your friend with glasses then feel like you need a pair, so you try theirs on, only to get immediately dizzy and blurred? Turns out you can actually leave those on for a while. Wearing glasses that you're not prescribed for won't damage your vision. It can make you sick, but that's just because of the eyestrain. Your eyes won't suffer permanent damage. You should still probably find a pair that works for you, just in case.
We have been told not to stare at solar eclipses because of the damage they can do to our eyes. This is actually....still true. Mostly true. But very mostly true; there's a small catch. If you plan on viewing the August 21, 2017 (woo!) or April 8, 2024 North American eclipses, or any future solar eclipse, you need to have protective eyewear. The only time if it is safe to sneak a peak at the eclipse is during totality - when the Sun is completely covered. But you have to be quick. The totality of the 2017 eclipse will last no more than 2 minutes and 40 seconds.
So even though hugging your face to the TV, reading in the dark, and peaking at an eclipse may not be as bad for you as you think, you still don't want to be reckless with your eyes. Staring at small text on your phone can put a strain on your eyes and make you sick, even if only temporary. Sleeping with contacts in could lead to an infection, and having a poor diet will also effect your eyes just like it will the rest of your body. Also, overusing eye drops will just lead to more irritation, and when you rub your eyes, don't rub too hard: intense rubbing could lead to broken blood vessels under your eye lids.
So now the myths are busted. Your are eyes are still delicate, but they can handle more than we think. And if you were absolutely dying to know, yes the raw steak on a black eye...it's a myth.
*New York Times, American Academy of Ophthalmology, Scientific American, ABC News, Look After Your Eyes, Good Housekeeping, Dr. Axe, Bembo, VSP, NASA, Astronomy., photo from Penn State