Never ever 'train to fail', always leave at least one in the tank. I think in many years of training I only failed 3 or 4 times, once was at PTC attempting a new PB for bench after a bench training seminar still traumatized by that, and involved some peer pressure to try for more.
Training to fail is bad for your state of mind I believe, as it does exactly that trains you to fail. Who wants to practice failing?? You should practice succeeding when you train, not failing. Failing repeatedly in training gets your mind and body accustomed to not succeed and accept it as normal to fail. For me missing a lift is not an option.