For those that are working and in school, how do you juggle it and not get burnt out?

I’m going back to school to finish my BS after an almost 10 year hiatus. I just registered for classes. Two I’m doing online, and one is Biology with lab. I have no clue how the F I’m going to do this without working less than 30 hours a week. Bio is Tuesday/Thursday at 8am and lab is Friday. The others I can go at my own pace… but it’s a lot of work. The university is also a 2-2.5 hour commute. I DO NOT want to fall behind. I was a lazy teenager that took nothing seriously the first go around, and I’m not doing that this time. I work full time currently- 40+ hours a week. 4 10’s and we stay late a lot. If I work a full day on Monday/Wednesday, that’s 20-22 hours. Slicing my already shitty income in half. I could do half days on the days I have class, so that would put me at around 35 hours. I worry that’s going to leave me absolutely wiped out mentally, and the August schedule is already made. I’m already burnt out and barely surviving some days. It would leave me with very little free time to myself. But I need the income. Idk what to do because we’re already short staffed af. Others have done it and had no problems… but I really really dislike this clinic. I’d leave in a heartbeat, but nobody else is hiring part time assistants unless I want to work night shifts. I would also do that in a heartbeat… but I can’t for health reasons.