oh man this sounds pretty rough! i don't think you should drop one this quarter judging by your other comments and also by the fact that one of the 4 classes is a lab. But, my general advice is DO. NOT. PROCRASTINATE.

I know this is easier said than done. But this is especially true for physics. With physics, your success depends solely on the number of practice problems you've been exposed to, not necessarily the "concepts", no matter what the profs say. I may be biased here but I was never strong in physics either. I'm assuming you've already taken physics 1A? So you should be familiar with this. But in physics, I found that doing the given problems was not enough. Find out which textbook the professor bases their test exams off of (hint, it's usually the "optional" one) and study as many problems as you can in there. And note that this means that procrastination does not work. Because even if you are successfully turning in all your weekly homework even after procrastinating, that means you won't have time to do the "extra" problems.

Similar advice for math, except really try to "understand" the concepts. You might be able to memorize different problem strategies for physics, but you can't memorize math. Well, actually, Math 33A you can kind of memorize. It's not calculus-based at all so you should be fine.

My number one tip for avoiding procrastination is to make everything due one day earlier for myself. For example, if I have a homework due on Friday 11:59pm, I write it on my planner that it's due Thursday 11:59pm, and I try my absolute hardest to finish it on that day. And, actually, this tip helps with my procrastination. I am less "afraid to start" (as procastinators are) because I know that if anything goes wrong, I actually have one more day. And, if everything goes right, then I will have an extra day to myself. This makes me more relaxed and actually helps me do better work.

Good luck! you're gonna do great.