Congratulations on narrowing down your career interests!
I'll be upfront about the fact that I personally have never been a Veterinary Assistant, but I was a Pet Groomer for five years and partnered very closely with our in-house veterinary staff and their practice when medical emergencies would arise with my clients (and I groomed for about five years, with one year of salon management).
I think the first thing I'd address is whether the role of a Veterinary Assistant is hard. I think in my experience, every job has aspects that are inherently easier for me than others. There may be things you need to do within that role that you find to be very easy, while your co-worker may find that aspect of the same role to be unpleasant or very difficult. This is the benefit of hiring for a diversified team, and if you join a practice that is mindful of what their team needs, they can find out what you personally enjoy about the job, and what you personally find difficult to make sure that there's always someone in your role that can step in to handle those tasks that others may not be as comfortable with.
In my time as a pet groomer, I can say that the thing that I found most difficult about the role were the parents. People are very emotional about their pets (including me), so delivering bad news was always a really difficult aspect of that role for me (while that wasn't the case for some of my co-workers). Not because I didn't understand the parents for being upset, but I'm an empath so I felt their grief, fear, and frustration very deeply which added an emotional tax to my day-to-day work that I originally didn't expect or prepare for.
Working with animals requires patience too. Even the best-trained animal is going to be afraid, uncomfortable, or irritable in that environment. Especially if something is wrong. They aren't like children or other people where you can reason with them when they're in this state. You'll need to be mindful of their safety, and the safety of your peers, when you're in a confined space with animals that may react in unexpected ways. This will require quick thinking, quick reaction, and leaning heavily on what you've learned about safety and pet behavior.
Working with animals was incredibly rewarding for me, despite the elements of it that I personally found challenging. If you're interested in learning more about what they do before making a final decision on whether it's the right path for you or not, you can always contact local veterinary clinics to see if anyone would be available to walk through some of the day-to-day with you. There are also usually 'a day in the life' videos that you can find online (on YouTube, for example) that might give you the information you're looking for as well.
(Former Pet Groomer & Dog Trainer)