Looking back over my training I think the biggest mistake I made was training to failure all the time. I would read everything I could on Arthur Jones, Darden and Mentzer.
Every set would take me close to death. It's a stupid way to train leading to burn out. Imagine if you were a runner and you mapped out a 3 mile course. Would every single training day would you try to beat your previous time? If you were a beginner that could be an accepted protocol but for an experience lifter it's nuts.
For almost 40 years I kept a training journal. I found working out like a lunatic without drugs I would burn out in 3 to 4 weeks needing a week off. Don't get me wrong I made good progress but taking every set to failure trying to get one more rep or another pound on the bar takes a toll.
In the past I would watch guys train that didn't use a low set HIT routine and terminating their sets prior to true positive failure thinking they didn't have a work ethic. Now I realize training to failure is a tool and it shouldn't be the only method used. I think think sets should so something like this.4 sets of 10. The first 3 should be hard but not killer. The last could be failure. So first set you might be able to get 15 but you stop at 10. Second maybe you could get 13 but stop at 10. The third maybe 11 but you stop at 10. Your last set you fail at 9 reps. This gets all the muscle fibers. If you do one set to failure you are not getting all the muscle fibers.