If you don't feel challenged, it's because you're not doing enough. Ballet should never feel comfortable. Comfortable is lazy! If you're comfortable when you dance, you're not pushing yourself hard enough. 100 % is not enough. You have to give 200%. One tendu takes years of hard work and will never be perfect. Everything in ballet is a challenge.
That's what happens nowadays with people working on computers. They can so easily fix things with their mouse and take out all the, 'Oh, somebody coughed in the background; we need to take that out' - or somebody hit a bad note. Those are all the best moments.