None of what you were told is correct, sounds like somebody doesnt know much about the topic. A bad trip, albeit random and unpredictable, can, for the most part, be avoided. Only take acid when you are feeling up to the journey. If you're going through a difficult time or have something that's been bothering you recently, it's not a great idea to take acid, it can really amplify your feelings of being paranoid or anxious/nervous. Also, next time you partake, make sure your set/settings good for the next twelve hours. You want to be in a comfortable set (your house or back yard, secluded wooded area, nature trail.) Also try and have just a few close friends, I find the more people you have to be aware of, the more difficult your time can be. A few trusted friends shouldn't be a problem, anymore and you can run the risk of situations arising or awkward interactions. Lastly, get a test kit if possible, ALWAYS test to make sure the product you're consuming is safe and indeed what it's been sold to you as. Using these three tips should eliminate alot of problems that can bring on the dreaded bad trip feeling. Hope all goes well for you in the future :D