What is a healthy dose of challenge?

When training people to become proficient or excellent in a given field, it is natural to question how rigorous or challenging the training process should be. On the one hand, we can recognize that if the training poses no challenge at all to the trainee, it is unlikely that the trainee will be able to improve in his ability. However, if the training is extremely challenging it can seem overwhelming or even dangerous.

I have found that a big factor in determining what amount of challenge is healthy is the perspective of the trainee. Without a level of commitment to learning and growing, the trainee can easily dismiss any amount of challenge as being too much. However, if the trainee is really serious about growing and advancing, even a seemingly overwhelming challenge can be taken as a valuable learning experience. 

This is why utilizing peer influence in group training programs can be effective, because if the bar is set high in terms of demonstrating individuals that excel through very rigorous training, it can naturally help the others in the group recognize that what seems to be an insurmountable challenge is actually a precious learning opportunity.