We trick ourselves into thinking that which is unpleasant must also be difficult, but that's not always true. Sometimes an unpleasant task is also difficult, to be sure, but sometimes a task is merely unpleasant without being difficult. I don't enjoy washing dishes, but I don't find the job particularly challenging. Sometimes the very fact that something is difficult is what makes it pleasant at all. My wife worked a jigsaw puzzle the other night. I find jigsaw puzzles both difficult and unpleasant. My wife enjoys working jigsaw puzzles precisely because they challenge her.
While she sorted pieces and fit them together, I wrote a story. Actually, I wrote the first draft of a story--I don't claim it is done yet, but at least the first draft is finished. I quite like this story. I conceived it as a challenge to my skills, to attempt to write something I wasn't sure I could create. I enjoyed writing that draft because I wasn't certain to reach the end.
When I declared my first draft done enough, I brought my self-satisfied smile to the table with the nearly complete puzzle spread upon it. I picked up a likely piece and tried to fit where I knew it inevitably belonged. Of course, my puzzle piece didn't fit there, so I tried the next most likely place. I failed again. Then I tried the next, with the same result.
I never did find where that puzzle piece fit; I ran out of patience before I ran out of places to try to put it. Eventually my wife fit my piece in with the others, patiently finding its spot with the others so that the whole picture took shape. Then she smiled a self-satisfied smile and looked at her work.
Difficult and unpleasant aren't the same thing at all. I suspect we are happiest in life when we work on the difficult things that are pleasant.