- When you have a project ($), you have to scrounge around for a student, and you may not find one that you like that's a good match.
- When you find one you like that's a good match, you may not have the money.
- When you have the money and a student, the timing may be weird. Like the money runs from March to March, but the student runs on the academic year. Etc.
THEN, should all the planets align and you can get the administrative details to work out, you have to figure out how to get their best work out of them. Some students need a lot of direction, some students hardly need any (and you maybe it's a struggle to squeeze info out of them), some students need moral support so you have to be a cheerleader for them, some blah blah blah. I find this a tremendous stressor and challenge. It literally keeps me up at night.
I wonder about my own advisors from grad school. Did I keep them up at night? Did they agonize over how to mentor me? Did they ever think about it? Was I a challenge? Did I stress them out?