Failure is a fine option!
When guiding a student through an exercise, I sometimes take them to the point of failure. This may be a note that is too high, an ornament/riff that is too fast, or a phrase that is too long. We need to see where our limits are! We need to occasionally fail within a safe environment, look at the failure, and learn. This is not forcing. Forcing is repeating the failure over and over, hoping for a better result. Banging away at a bad thing is often physically harmful and demoralizing.
When working with high notes with newer singers, for example, there is much to get in order. There is physical strength, the coordination between different laryngeal muscle groups, the vowel, the volume, the pitch, interfering muscle tension, fuzzy goals, inexperience, and other challenges. The teacher and the singer must have a goal for an exercise, and also be very clear about what part of the result is good or bad. Sometimes a burning barn is beautifully lit!
Singing is a physical activity, involving muscles and coordination that is unlike any sport, yet the principles of vocal training have a lot of similarities to sports. In weight training, exercising a muscle group “to the point of failure” means that you stop and do something else. It does not mean that you rest for a minute and then jerk the weight up into one more rep by any means necessary. It doesn’t mean doping up and coming back to it tomorrow while the muscle is still repairing itself. It doesn’t mean doing the exercise with sloppy form for the sake of more impressive stats. You just stop, take notes, and come back to it at the right time, on Nature’s schedule.
The willingness to go to failure is required in order to increase your abilities, or even to stay in touch with your current abilities. Young athletes understand this very well. Young singers often do not, partly because of a perfectionistic culture in musical training and performance. Many teachers are too cautious, or don’t know what typical limits and potentials are, or want to keep things easy emotionally.
If a student is having a hard day, or is weary or sick, I don’t go looking for their outer limits. On those days, we work with “middle and medium” things. We treat ourselves with kindness, and do what we can do. Teachers have two main roles here: instructor and model. We need to show students (with our words and deeds) how to stretch themselves, and also how to take care of themselves – how to adapt to suboptimal days and go for it on the great days.
Learn how to fail successfully, and you will learn how to grow.