My entire fourth year was ridiculously hard. My program, microbiology and immunology, had 400-level courses that were GPA killers. I had to take two bacterial pathogenesis courses, a virology course, an environmental microbiology lab course, and a microbiology genetics lab course. I was lucky to get an A- out of all of them, except the virology course where I got an A+ and the environmental microbiology lab course where I got a B+. I busted my ass off day and night studying. I've never studied so hard in my life, not even for med school. I managed to boost up my 4th year GPA taking easy electives, but it was still my worst year in my undergrad in terms of GPA (although better than my 1st year in terms of % average). On top of all that I had to work 20 hours a week to pay for tuition.