If you want to be a beast, you need to train like a beast. Forget this garbage of overtraining....the only way for your body to grow and become the beast you want it to be is to push it into territory it has never been before. Everytime you step into that squat rack or lie on that bench you need to be pushing yourself for that extra rep and that extra 5kg on the bar. Using the Olympic lifters mentality is the way to go. Day in day out for up to 4 hours a day they step onto that lifting platform and they clean, they press, they squat and snatch and then the next day they come in and repeat it again, then the next day and they do this everyday without ever moaning or worrying that they won't grow. Just think about it, do you really think that you will grow from doing a few sets for each bodypart rarely adding weight to the bar versus attacking the weight, making your body scream to stop yet your mind pushes you over and over again. Your muscle has only 1 options. It will get stronger and bigger because you haven't given it a choice.
No one would argue that some rest helps, but think twice when you think you are overtraining and need another day off. Provided you eat plenty of good food with truck loads of protein and drink plenty of water your body will respond to it been pushed to where it never has gone before. Get in that gym and start training with intensity and with a beast attitude and you will be surprised at how your body responds.