Work is the last place most people feel comfortable getting emotional.
Nonetheless, it is very common for things to feel all too much in this area of life from time to time. It is silly for it to be common knowledge that having a job can be very stressful, but at the same time, expect employees to maintain their professional composure without letting their feelings slip.
It is especially difficult to keep it together when you are new and inexperienced in a role. Dealing with mistakes, embarrassment, and coworkers who may not always be the most sympathetic can prove to be a challenge for someone who is just finding their feet. As a result, it is more likely that a person is going to be emotionally overwhelmed at this point in their career, having not developed as many coping mechanisms to deal with this. It is all a learning process.