I've experienced similar things and always put it down to boredom. My younger self might still have found it interesting and novel. Now I just view it as a chor

I've experienced similar things and always put it down to boredom. My younger self might still have found it interesting and novel. Now I just view it as a chore. I've lost some of that intrinsic interest which I think contributes. If I work on more interesting problems the issue is less pronounced.