Physiology and Micro together will probably be a heck of a handful. It's completely doable but you have to know how you study and retain info. If you absolutely must
take them together and need a full load, choose a course or courses that will further your educational goals while being less heavy on the studying. By the time I took Micro, I'd already had a good, solid education in the sciences, so I found it to be relatively easy. It was still one of the more difficult courses, but by then, I'd already figured out my learning style and exploited it fully.
Probably the hardest thing you'll have to do is find out where the courses have some commonality and where they overlap, you study for one and the other at the same time. This won't happen very often though.
If you're lucky enough to have a course syllabus that breaks down each assignment/topic by each day or week, use it to get ahead by about 1-2 weeks in the reading and then stay 1-2 weeks ahead. Then you'll see the material again in class and then review. By the time you've gotten to an exam, you'll have seen the material at least 3-4 times. You'll know it.
Physiology is very interesting. So is microbiology. It's fun to learn what the little beasties are, how and where they grow best and under what conditions.... and learn how to kill 'em. If you're getting to do sensitivity testing or testing with common household cleaners and compounds, see if anyone has any tea tree oil.