As hard as I thought? About 100 times harder, actually.
Nothing about the curriculum is exceedingly difficult, but you have to have a good handle on Anatomy and Physiology and you have to be able to learn to think critically.
It's not about "what is the definition of xyx" It's about "Here's your patient, they are exhibiting xyz symptoms, what do you do"
You not only have to learn the material, you have to understand it, completely. Then, you have to retain it and use it in the future.
Everything you learn is fair game on all future tests, and several answers on each question will be "correct", you need to pick which is the "most correct".
Get a good handle on medical terminology
and kiss your social life goodbye. If you do those two things and study your face off, you'll be OK.