I'll point out only those that I once believed. It becomes rather funny when you start educating yourself about something and whilst in the process you look back and almost have the urge to laugh at how differently you used to think of a certain things. The thought of weight loss used to make me nauseous. I thought it was impossible for me to begin with, and it meant not eating what I love. I was so wrong about everything.
First off, I started out with believing that starvation would do the job nicely. It actually does though rather painfully but you wouldn't want to damage your organs that way—the worst way to think of losing weight when you're thinking long term.
Calorie counting: I mean you really have to have so much leisure hours at hand to get that done and even that wouldn't guarantee if you're doing it right. Waste of time.
Carbs makes me fat: Initially I was told to cut down on carbs completely, leading me to believe they made me fat. After trying for two weeks I knew it was load of bullshit—If eaten in the right quantity, they won't cause you to gain weight.
Skipping meals: Good God what was I thinking?! Skipping meals is definitely not a good idea. To
lose weight and keep it off, you have to reduce the amount of calories you consume and increase the calories you burn through exercise. But skipping meals altogether can result in tiredness and may mean you miss out on essential nutrients.
Not eating before workout: I was stupid enough to think not eating before going to gym would help me burn more calories, it made things worse for me instead. Obviously having not eaten anything pre-workout I didn't have the energy to move about and work out properly, it made my head spin and that was that. Thanks!