Diet is without doubt the hardest part of any training programme, this is the majority of peoples stumbling block when it comes to achieve that dream physique. 
When you are training the chances are you will be consuming 6+ meals a day, none of us have the time to be slaving in the kitchen all day so an easy way to get round this is to cook all your meals at once. You can cook a days or even a weeks worth of meals all in one go, simply refrigerate or freeze and get out when necessary.  
Another benefit to prepping your meals if that when you have all your meals set out and already cooked you have no need to rummage through the cupboards looking for something quick to eat in order to satisfy your hunger. 
By prepping your meals and following a healthy diet that fits your required macros you will notice huge differences in a short amount of time. 
There are various cool bags available on the market which you can put your meals in for the day and they will stay nice and cool, ready to eat.