We are all given lots of "do" and "don't" advice when we're growing up--even after we're grown up, depending on the company we keep. Some of it is outright lies, or at least untrue, such as, "If you swallow your gum it will just stay in your stomach forever." Some of it is true only sometimes, such as, "Don't go swimming if you just ate a big meal." Sometimes you go swimming after eating, and your fine, but sometimes you start getting cramps and you have to stop.
A lot of it, though, is legitimately useful information, like, "Don't mix bleach with ammonia." If you did this, you would create chlorine gas, which can be deadly in an enclosed space. I once got a breath of chlorine gas in high school chemistry, and it felt like my lungs were melting. It's probably the least pleasant thing that has entered my lungs.
The fact that we're given so much supposed advice, and not all of it is true, means that we start to become dubious about all of the advice. You say to yourself, "Hey, they were totally lying about the watermelon seeds. What if they were also lying about putting metal in the microwave?" The natural inclination of such a curious child would be to put metal in the microwave to see what happens, and then maybe the microwave explodes or something. I'm not too sure, because I know better than to put metal in the microwave.
Because these things are supposedly bad ideas, youv'e never seen anyone do them, so you have no idea if they're true or not. Your mom says that you'll get cavities if you don't brush your teeth, so she makes you brush your teeth twice a day, and even makes you fucking floss. Then you start to become dubious about these so-called "cavities," and get lazy about brushing your teeth, and the next time you go to the dentist he tells you that you have three cavities. Then you get the additional learning experience of what it is like to get a filling.
Ideally, at some stage of your adulthood, you have learned that sometimes the advice you got growing up really was good advice, and that it would be a bad idea to go against it just to see what would happen. Personally, what I do is that I will ask someone who I think would know the answer, and be able to explain the reasoning behind it.
After learning a lot of "good ideas" and "bad ideas," and what things are "safe" and "unsafe," you start to develop a kind of safety intuition: you have a funny feeling that what you are about to do is probably not the best idea in the world, but you're not entirely sure why. You can respond to that nagging feeling either by brushing it aside (if you are drunk, this is the more likely scenario), or by trying to think about what could be wrong with the picture and how it could be made a better idea.
This is why some of us have a billion alternate timelines where we are "that guy who dies in a stupid, preventable way that is entirely his fault." (Ladies, in these alternate timelines, you are male.) The difference between listening to your intuition and disregarding it is sometimes the difference between waiting for your lava lamp to heat up on its own, and heating your lava lamp on the stove enough for it to explode in a shower of glass. So, keep that in mind the next time you are about to combine two different cleaning products with the expectation of creating one Super Mega Cleaning Product.