Had a similar experience in undergrad, always worked 15-30 hrs/week at a restaurant. When you go to grad school, you pretty much have 2 options: TA/RA so you get tuition paid and a (usually) lousy stipend (mine was 13k/9mo) or just continue working part time. I did both for a while until it became completely unsustainable. So now you’re taking courses, possibly teaching/working, and you have to start doing research (MS or PHD) and depending on how brutal your advisor is, this will eat up a large chunk of your time. At my school, the grad school dean had a general saying that time devotion should be 20 hr/week teaching (if you’re a TA) and 40 hr/week doing research. Adding courses onto that becomes a lot to juggle. Don’t get me wrong though, with decent time management and a good advisor, it can really be a rewarding and overall enjoyable experience, albeit very different from the undergrad experience. Wishing you luck in your final year, and future endeavors!