One of the more painful things to learn as a faculty member is to accept that you will do some things badly. There are too many things to do, so you can’t do them all well. What should you do badly?
As an undergraduate, the scope of work is reasonably precisely defined, and problem sets have relatively simple solutions. I finished things on time or even early, and I seldom felt guilty for not studying.
In the first year of graduate school, problem sets are much harder, but they still all have solutions. That there must be a short solution to every problem on an exam is generally the most important thing to recognize in attempting to solve them.
Later in graduate school, identifying a solvable problem becomes part of the research effort, but you can focus all of your effort on that work and so do everything well. For me, there was little need for time management, since I had loads of time.
Even as a postdoc, when I’d started to do many more things at once, I still had few responsibilities aside from my own work, and so I could do everything well. And basically what you need to get done is just defined as what you actually get done.
Faculty life is quite a bit different. I’m making real commitments to people. And then there’s teaching, and reviews of papers and grants, and committees, and letters of recommendation or evaluation. My personal research efforts often are pushed aside in favor of rush-rush collaborative work. Or I’ll spend weeks doing little but read and comment on others' work.
There’s just too much to do and not enough time to do it as well as you’d like.
So, what should I do badly?
Well, definitely not my own research papers; those will outlast me. Maybe some day someone will read them. Similarly, not seminars I give, as through such research talks, I may gain a reader. I suppose family, health, and sleep should be mentioned here. And biking.
Committee work. If someone says, “I enjoyed reading the report you wrote”, you’ve clearly been focusing on the wrong things.
Reviews of papers. Sure, I want to help out the authors, but I can’t be doing their research for them.
Teaching. If you try to do your best, you’ll do nothing else. The students may notice the difference between just dusting off last year’s notes and actually preparing (and fixing past mistakes), but will they really learn much more in the latter case? To learn, they must struggle a bit, e.g., through the errors in my notes. Is that just a rationalization?
Reviews of grants. Someone’s livelihood is at stake, but does it really matter if the text of my review is awkwardly phrased?
My own grant. Some of my colleagues will start writing a grant months in advance. I say: if you start months in advance, then you’re going to spend months on the thing! You should start as late as possible. A perfect score on a grant is an indication that you spent too much time on it. The best grant score is the worst possible that still gets funded.
As I said, it’s painful to do things that you know are crap (i.e., could be much better). It’s hard to accept one’s limitations.