Keep your résumé to 1 page. Employers will only read the first page, and you don’t have enough experience to justify a 2-page résumé.
Don’t spend so much energy taking notes during lectures. Ideally 100% of your attention should be spent on listening to the professor and understanding their train of thought. Many students make the mistake of writing everything the professor says, leaving little room to learn in the moment. Learn it right the first time, and when studying for exams either the prof will upload their notes, or you can read the textbook.
Exercise. Everyone has time to exercise. You will feel better, have more energy, and discipline in one area of your life will bleed into all other areas.
Don’t apply to so many jobs. I am always afraid of getting matched with a bad company, so I end up applying to way too many jobs, getting too many interviews, and spending too much time in the Tatham Centre. I end up with offers from companies I would never see myself working at, and end up wasting my own time. Be confident, and only apply to serious jobs. You’re a software engineer in an era when software is eating the world.
Treat co-op as a vacation. Go out, spend some time with your friends, and spend some money you’ve earned. The Waterloo program doesn’t give you any vacation. It’s a constant grind between work, school, looking for jobs, and moving city to city. However, during co-op your work is bounded to 40 hours a week, so you should use your spare time to have some fun.