By working out you can eat what ever you want to.
Of course you can eat whatever you want, if you don't care how you want to look. Working out does not give you an open license to consume as many calories as you want. Although you will burn more calories if you workout than someone who doesn't, you still need to balance your energy intake with you energy expenditure.
If you take a week off you will lose most of your gains.
Taking one or two weeks off occasionally will not harm your training. By taking this time off every eight to ten weeks in between strength training cycles it has the habit of refreshing you and to heal those small niggling injuries. By having longer layoffs you do not actually lose muscle fibres, just volume through not training, any size loss will be quickly re-gained.
By eating more protein I can build bigger muscles.
Building muscle mass involves two things, progressive overload to stimulate muscles beyond their normal levels of resistance and eating more calories than you can burn off. With all the hype about high protein diets lately and because muscle is made of protein, it’s easy to believe that protein is the best fuel for building muscle, however muscles work on calories which should predominately be derived from carbohydrates.
If I'm not sore after a workout, I didn't work out hard enough.
Post workout soreness is not an indication of how good 
      the exercise or strength training session was for you. The 
      fitter you are at a certain activity, the less soreness 
      you will experience after. As soon as you change an exercise, 
      use a heavier weight or do a few more reps you place extra 
      stress 
      on that body part and this will cause soreness. 
Resistance training doesn't burn fat.
Nothing could not be further from the truth. Muscle is 
      a metabolically active tissue and has a role in increasing 
      the metabolism. The faster metabolism we have the quicker 
      we can burn fat. Cardio exercise enables us to burn 
      calories whilst exercising but does little else for fat 
      loss afterwards. 
Weight training enables us to burn calories whilst exercising but also helps us to burn calories whilst at rest. Weight training encourages muscle growth and the more lean muscle mass we possess, the more fat we burn though an increased and elevated metabolism.
No pain no gain.
This is one myth that hangs on and on. Pain is your body signalling that something is wrong. If you feel real pain during a workout, stop your workout and rest. To develop muscle and increase endurance you may need to have a slight level of discomfort, but that's not actual pain.
Taking steroids will make me huge.
Not true, strength training and correct nutrition will grow muscle. Taking steroids without training will not make you muscular.
Most steroids allow faster muscle growth through greater 
      recovery, while others help increase strength which allows 
      for greater stress to be put onto a muscle. Without food 
      to build the muscle or training to stimulate 
      it nothing will happen. Most of the weight gain seen with 
      the use of some steroids is due to water retention and is 
      not actual muscle.
Strength training won’t work your heart.
Wrong!! Strength training with short rest periods will 
      increase your heartbeat well over a hundred beats per minute. 
      For example, performing a set of breathing squats and you 
      can be guaranteed that your heart will 
      be working overtime and that your entire cardiovascular 
      system will be given a great overall body workout. 
Any intensive weightlifting routine that lasts for 20 minutes or more is a great workout for your heart and the muscles involved.
I can gain muscle and lose fat at the same time.
Wrong. Only a few gifted people with superb genetics can 
      increase muscle size while not putting on body fat. But 
      for the average hard gainer, they have to increase their 
      muscle mass to its maximum potential and then cut 
      down their body fat percentage to achieve the desired shape.
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 The vast majority of myths about weight gain are mostly 
      passed down from
The vast majority of myths about weight gain are mostly 
      passed down from 