What is your motivation if you are indeed seeking to ordain as a monk or a nun?
I would hope it would be for the best reasons; however, I have read so many autobiographies since the 1990s of so-called modern seekers most who failed to remain robed that I should address motivation first.
If you become a monk or a nun in the Buddhist tradition called the Sangha then your motivation should be seeking Enlightenment for yourself while being a monk or a nun in Buddhist robes.
However, people become monks or nuns for much different reasons. Some reasons are for the fad of it, professional aspirations, supporting politics, supporting the underdog, to stand out from society, attain fame, get money, emotional satisfaction, making history, legitimizing views, infiltrate and conquer, escape, to help others, gay rights, women's rights, feminism, and many others.
Popular causes highlighted in Buddhism tend to attract people's attention. Countries that have troubled histories in Buddhism tend to polarize people's views regarding Sangha behavior and authority. History is often ignored in light of headlines.
Those seeking ordination need to really take the time they need to explore their motivation. If you are politically or fashionably orientated then you are facing more obstacles if you indeed achieve the goal of becoming ordained in robes.
Seek out stable long standing communities of Sangha to observe, be observed and understand how they work, practice and live. If you go into the robes without knowing the language, culture, history or even the basics of how you are expected to live and survive in robes then you are indeed in for a really rude awakening and may become frustrated and negative in your own life.
Mental health in those seeking ordination, you must be conservative here. People do your work on yourself. Make use of therapy and therapists before you try to join a monastic community. Have plan of safety if you suffer form chronic mental illness. If you are good at putting it in place, taking care of your needs diligently then you should have no problems in your monastic life.