Stress
The biggest stress is whether your job as a film critic is actually bringing you enough money to live. You'll feel very stressed when the landlord comes knocking on your door asking for the rent and you don't have it.
There are also deadlines to worry about if you're working for an actual paying review job. Watching a movie is great, but if you have trouble following that with your opinion in written word form, this is going to be a difficult job for you.
Then there are the jerks. You know the ones. People who don't just disagree, but disagree in an angry, aggressive, borderline unhinged way. Why? Because you thought that the latest Star Trek film was "good, not great."
Thankfully, though, dealing with them is usually as easy as a quick click of the delete button. But if you're sensitive, we'd suggest not checking out the comment sections of your reviews. For some reason, people don't usually go through a webpage's lengthy commenter sign-up process to tell you "good job."