Scared to quit (CAN)

So basically I worked here for a few months leading u0 to summer break (where I went to my hometown for 4 months.) Now that I'm supposed to go back I'm not sure if I want to keep working there. The work environment at that location is super toxic and i'm also just super busy as a student this year. I've got a couple interviews lined up already with other jobs.

I'm just super scared to quit. Am I gonna be in deep trouble for doing so? I was planning on sending an email a couple weeks before my return date. What should I say in this email to prevent ending things on super bad terms?