For me, rushing was hard because it's just a really, really draining procress, even though I actually really liked it. My campus has 15 sororities, and you have to go to all 15 in the first two days, 10 the next, 5 the next, and 3 the next. Some people can handle constant social interaction for 5 days, but for me, it was just exhausting! When I got back to my dorm, I IMMEDIATELY went downstairs to the boys' floor every night just to get some testosterone back into my life, and then took a forty-five minute shower just for some alone time!
Rush can also be really hard emotionally if you get cut from a group and really don't understand why. This happened to some of my friends and made them really upset, and I got cut from a few sororities and felt pretty sad about it--the whole "Why didn't they like me??" thing. That's really not the way to look at it, though. The truth is that they weren't really the people I would have gotten along with. I definitely found my sisters in Alpha Chi.
Good luck! Don't worry too much--I actually really enjoyed Rush. I loved getting dressed up and I liked carrying on the conversations. I liked it so much that now I'm the Recruitment Chair for my sorority!