In a class this big, it's inevitable that some of you will have a major life problem of some sort. Examples include being sick for a week or more, disabilities, family or housing issues, course loads that prove harder than you thought, deciding that you are in the wrong major, and so forth. Because high school is easier, issues like minor disabilities, test anxiety, and bad study habits sometimes don't cause problems until college.
Sometimes people create problems for themselves e.g. by making bad registration decisions or by too much partying. Most of the following advice still applies. You'll get less sympathy but don't let guilt stop you from seeking help.
You've probably got some ideas about things you can start doing on your own. E.g. review missing homeworks, even if it's too late to get official credit. If you miss an early-morning quiz, don't stay up so late, get a better alarm clock, and/or get a planner so you don't forget quiz dates. But if it seems like what you can do is not enough, seek help.
First, keep firmly in mind that your problems can be solved. You'd be surprised how many successful senior professionals had a rocky semester way back when and bounced back to do great work.
Second, keep the 173 course staff informed, so that we can be part of the solution. Make sure to exploit resources such as discussion sections and office hours.
Third, remember that you can't do math if you are too tired, not eating properly, drinking too much coffee, etc. Treat your body decently. For example, go to bed at a reasonable hour before a morning exam: extra studying is nowhere near as important as being able to think properly.
Fourth, keep a flexible attitude about whether you've chosen the right courses, or even the right major. If your load is unmanageable or your courses aren't making you happy, something needs to be changed.
Finally, here are some useful sources of help on campus.