In the past, I have pushed myself in gym sessions and even during certain bodyweight training sessions to the point where I couldn't move anymore in a particular exercise so in other words trained to the brink of failure. I looked at that as a sign of knowing what it's like to have that warrior mentality and pushing through pain and giving it all I got. All it really got me was in fact pain, not sore muscles but actual pain and still feeling the effects of some of those sessions to this very day in places like my right shoulder, ankles & even my elbows.
Going to failure basically means you do so much until you can't move anymore in an exercise like the bench press, deadlift, push-ups, squats or whatever. You keep going until that last rep is so freaking tough, ever inch hurts and its the ultimate struggle. Many take this as a sign that it means you'll get stronger next time around. Don't get me wrong this is true to a degree but for overall development from my own experiences and being around others who've done it, it can actually weaken you because when you go that hard, you're not just stressing the muscles, you're also putting even more stress on the joints and ligaments and the chances of anything tearing are greater when you do go to failure workouts.
Going to failure depletes your energy both mentally and physically afterwards or even during on some occasions and when your energy is depleted, this can lead to a series of problems and can take you out for often times weeks for complete recovery. The type of training ought to be giving you or help conserve energy regardless of how strong you are. This mentality for going to failure is usually by hardcore fanatics either in sports or the gym or whatever it is they're training for. Me personally I can't afford to get injured or something worse because I do have a job, a house I take care of and need to pay for things to help stay afloat when its needed. When you're injured, you can't do the things you want to do, recovering from injuries can be unpredictable and if you have a job where if you're injured and can't do the tasks, you're not getting paid.
I don't train to failure because I need the energy to stay focused in what I need to do. I hate not being able to train and when you don't have the energy to play with your kids, can't squat without feeling some form of pain, not move with efficiency; it'll make you miserable. You need that energy from beginning to end so the very things that are important in your are possible to accomplish.
There is a fine line between a few aches but severe pain is a miserable thing to have. Training to failure breaks down the muscles way too much and the recovery time can take longer than you'd like it to be. I play with exercises every single day and have for nearly 12 years ranging from 5 min. to well over an hour and still have energy to do things with the people I care about. Be smart when you train and train to conserve energy whether you're a beginner or advanced do what's best for you and make the most of it without suffering the consequences of overtraining and putting your body at risk. The body can only take so much regardless of how you set your mind to. The idea is be as pain-free as possible and have strength during and after your playouts.
Playout, Don't Workout.