Looking to start CNA training soon, worried about some things

Hi, my name is Paige and I'm 22 years old. I've been interested in the field of nursing since I was 14 years old, and recently discovered a trade school by my house that offers a medical assistant/CNA training program. At the moment, I'm trying to find a job at a kennel or vet clinic (I love working with animals), and my plan is if I can't find a job before next year, I'm going to apply to the school and take the CNA training, and hopefully get my certification afterward.

I really like the idea of working as a CNA. I like the idea of helping sick and elderly people for a living, and being able to care for those who can't help themselves. If I wind up really liking the work and working with people, I'm thinking I might look into going back to school and becoming an LPN or RN after I've saved up some money/have my own car/etc.

Now, I know that CNA can be difficult work. My cousin worked as a CNA for a few years, and she always said that even though it was very hard, she loved it and it was very rewarding. I feel that I can handle most of what the job involves; cleaning up patients, having to lift them, etc. However, the only thing I am a little worried about - and I hope this doesn't make me come across as selfish or unfit for the job - is having to deal with overly aggressive or sexual patients. Now, I realize some of these patients can't help it, that they suffer from dementia or similar ailments and don't realize what they're doing. But at the same time, I am a little worried about possibly being injured or molested by a really difficult patient. My question is, how often does this happen, patients seriously hurting you or groping you, etc., and what kind of precautions are in place to prevent it?