Whether it is teaching a class, coaching a sports team, or taking on a new professional responsibility, sometimes I think there are two main types of challenges out there.
One - the kind that you are extremely well prepared for, the processes and outcomes are clearly defined and reasonably predictable, and success is to a very high degree linked to effort - the harder, and to some extent longer that you go at it will determine the results.
The other kind of challenge is new or uncharted territory for you. The long-term result may be known, but it is certainly more intangible. You may have some kind of understanding of the 'how' part of the task in front of you, but you quickly discover that there is not a set pathway to follow. And long-term success may not at all be tied to how 'hard' you work, it could be that some new type of insight and creativity is necessary. That may come in ten minutes, or it may not come at all in five years.
But ultimately it seems like the most rewarding kinds of challenges contain elements of both types. With enough predictability and process to support making steady and incremental progress, coupled with a nice batch of uncertainty and excitement that can make the task more challenging and fun. Some folks will naturally gravitate towards one type or another, but it is pretty unusual for someone to always prefer routine and repetitive assignments, or always choose complex, challenging, and unpredictable jobs.
I am thinking about this blend, and the best way to ensure that organizational job design can be flexible enough to support both kinds of people, and both kinds of roles, while meeting the needs of the organization and people's desires for meaningful work.