Work is Rewarded with More Work

That's what one of my professors said to me when I visitied campus after graduation. I finally got a job in my field of study, I didn't know what was in store for me at the time, and he was telling me about his gigs and classes and how he and multiple colleagues have to work in two universities just to make ends meet. I asked how he was able to get so much work. He said he was given a few classes and then when he did well enough on those he got to teach more. I then asked if he gets tired of it. He said yes, and he wishes he didn't need to do so much. But then he said:

"Work is rewarded with more work."

No matter how much he would try to manage his time and consolidate his traveling plans, no matter how much work he completed, he would always be given more work to do. And it's exhausting.

...

Fast forward to now: I'm writing this on March 24, 2025, when I should be going to work, but I'm very much not motivated to go to it. I've worked at this place for three months, and it's been going slow. I've only gotten a few students and I'm still only going twice a week, with risk of that going down to only Mondays for the month of April. At the same time, now that I finaly have some (temporary) students today, I've been booked for several hours straight. That's great for my income, but that also means I either have to hurry to the last bus of the night or take an Uber (which would be about $20). I already need an Uber today, and was hoping to get there early so I could catch up on notes from past appointments and personal things while waiting for my students, but unfortunately that's not happening. I thought I could work well with this schedule because it's in the evenings when I feel most awake, but now every time I wake up on a work day, I dread getting out of bed. 

I'll be rewarded with more work if I do a good enough job, right? That's what I want, right? But is the work even rewarding? I was hoping this would be my big break in the music and teaching industries, but now it seems like I'm being tied down more than anything. Is the work my professors are doing rewarding to them? If so, how do I get to that point?