So this is a massive problem that I see on a regular basis in the gym with people not achieving results. Obviously there are other factors such as training structure and diet, but intensity is key for maximum impact. If you train with an average amount of effort, you will only get an average outcome. You need to train with the intention of getting results and this means training at an intensity that takes you beyond the norm. When I train, I lift to failure almost every set, unless I am working on gaining strength which requires a different approach. When I say failure, I mean you could not possibly lift the weight beyond the number of reps you are aiming for. You cannot expect change without making a change.