The bulking and cutting strategy is effective because there is a well-established link between muscle hypertrophy and being in a state of positive energy balance. A sustained period of caloric surplus will allow the athlete to gain more fat-free mass than they could otherwise gain under eucaloric conditions. Some gain in fat mass is expected, which athletes seek to oxidize in a cutting period while maintaining as much lean mass as possible.
When lifting it is essential to focus your mind completely on the muscle group you are attempting to work on. This makes sure that you are actually using the target muscle to lift the weight rather than accessory muscles or even momentum. This skill will develop with time, and as you progress in making that mind to muscle connection, your workouts will become much more productive and efficient.