Some of us get to the point of fatigue, cluelessness and increased hope for some miraculous breakthrough or salvation in our careers.
Most days on the job, one would generally hope to perform excellently for career fulfillment and fair appraisals. Somedays even going out of the norm to do that extra for a little more value added. At certain times one is expected to perform a task, meet and exceed expectations in completely unfamiliar territory. That's a different ball game and a major challenge altogether. Several hours and sometimes days with no meaningful progress in sight, the hopelessness sets in. After several diligent, dedicated efforts, there's the breakthrough and eventual success.
Though interestingly this situation keeps reoccurring... Confidence has developed in your skill set and abilities. Thus presenting more opportunities to exercise your thinking faculties. Every new task becomes easier to deal with. Decision making is more timely and more value is given towards your inputs.
In conclusion, challenges are factors in life that help teach you, build you, improve you and prepare you for the next level. Welcome them, the final result depends on how you perceive them.