Rest days

Weight training is simply about breaking the muscle down during a workout and it will repair itself and grow bigger with adequate training and recovery. Every time you train, you are actually tearing the muscle(s) and these tears become repaired,hence the muscle becomes bigger and stronger. Bodybuilding is just the body's ability of adaptation to stress to grow because it has no choice but to as you are demanding it to by putting it through its paces where it will answer and match your intensity. Depending on how hard you work, the reflection will be mirrored by your body.  

Sufficient rest is vital. I would advise a maximum of 4 to 5 days of training for anyone looking to reap the best results for their body. The muscle only grows when it is not being worked, so there is no point to exercise 7 days a week thinking you are being dedicated when in turn you are just damaging your body,  not allowing it to heal and repair itself. Furthermore, the stress hormone cortisol is released in a state of training which is normal but you want to keep this at a small amount and only for workouts. 

Tip : Take a rest day after each workout day or if you can't do that, ensure at least 3 rest days are in your week. On rest days, enjoy yourself, do something fun and relaxing like going to the park with friends or someone close to you. Nothing intense, just a light walk the next day will stimulate blood flow to the muscles feeding them with nutrients allowing them to grow.