Training to failure can have its benefits. It allows you to attempt a weight that you must struggle with but probably won't get. Whether you are attempting your 10th rep with something that you normally never go over 8 with, or you are attempting your 3rd rep with something you never go over 2 with. It's good on a couple levels. Mentally you've just attempted something that you've never done before. So, in a way it breaks new ground and you get to prove to yourself that while you may have had some apprehension with that rep, or that particular weight you overcame it and tried anyway. Also, physically you get to feel that next weight, or rep and you prepare your body for what is inevitably to come.
But, I caution you that training to failure on a regular basis is a very bad idea. use this method the way you might use negatives...that is sparingly (negatives are also hard on the body). Training to failure is also hard on the CNS (central nervous system) and can cause burn out, or become over trained. I suggest training to failure in a limited capacity perhaps once a week at most. I use it only a couple times per month with selective movements.
Also, keep in mind that you can create an incredible physique without ever going to failure. It's simply one more technique like all the other techniques. If you use it do so sparingly, if you never use it not a big deal.