I think having challenging work and receiving praise for what you have accomplished can be related but they aren’t necessarily. You could receive praise fore doing menial work just like you could for doing challenging work. If you feel you are doing challenging work and are receiving no recognition for it that could really ruin your motivation. Alternatively you could be getting a lot of praise for doing regular work. It really depends on what drives you. If you care more about the recognition, then doing challenging work won’t really matter. If you care more about the challenge then you won’t care if you get recognized or not. Personally, I like a balance of both. I like to be able to challenge myself and still get the occasional pat on the back for my accomplishments. I do find it important to feel valued. If I’m putting in extra hours or jumping through hoops then I would like it to be recognized in order for me to feel like i’m valued as an employee.