I recently realized that a big weakness of my workouts for the past couple of years has been a lack of intensity. More specifically, I would give myself a pass on half-assing a particular set by telling myself I'd make up for it by adding another set or another exercise to the end of my workout. This had the double effect of making my workouts longer and decreasing the effectiveness of each individual exercise I was doing.
I realized this because I am now working off of a set plan, where I perform a specific number of sets with a specific number of repetitions in each set. This framework takes away my ability to say to myself "that set was kind of lazy, I'll make up for it at the end of the workout." Now I have to approach every set and every rep with the attitude of working as hard as I can and maximizing my intensity.
This has really improved the quality of my workouts. With no way to make up for a bad set, I just have to make sure I don't have bad sets. Sure, there will be days when I'm not able to do as many reps or as much weight as I'd like, but as long as I approach every exercise with the attitude that I'm going to give this exercise every ounce of effort and intensity that I have, I'll end up with a darn good workout.
So, even when I'm done with this program, I'll always go into the gym with a clearly defined plan for which exercises I'll do, how many sets I'll perform and how many reps in each set. That'll keep me from making excuses for myself and give me the focus I need to get the best workout possible.