I'm not a model so I can't give direct advice as I would have no idea how it feels to be in front of a camera like that, but I have Generalized Anxiety Disorder (GAD) and my EX who was a model on MFC and Streamate for two years had Borderline Personality Disorder (BPD) and severe anxiety. We used each other as support and she would tend to break down a lot easier than I would due to her fear of being on cam, but it's what made her happy. Here's a few things she did to get through those years:
1. Seek an accountability partner. Struggling with depression and anxiety can have various levels of incapacitating someone. Whether it be damaging to their work life, social life, family life and so on, having an accountability partner can help to keep you on track with smaller daily goals which helps your overall mindset when you know you can achieve small steps towards a final product. This partner can be another model, it can be a regular viewer, it can be a family member or it could be just about anyone that you know will understand that you'll need regular checking in on.
2. Set your limitations. When my EX first started, she didn't really know what she was doing and would just do about anything for the viewers within an acceptable tip range. At one point towards her 8th month point, she was in a situation which made her feel very uncomfortable, stopped being on cam for three months and struggled to get back to a healthy mind frame. She came up with clear rules, what she would be comfortable with doing (such as no Skype whatsoever) and how long she would be willing to do whatever action it was.
3. Be open about it. Viewers can quickly tell when the mood is wrong and/or bad and keeping it secretive can lead to even worse reactions especially when a viewer lashes out, people leave and you may be stuck thinking you're doing something wrong. You don't need to tell everyone everything, but letting people know you deal with anxiety and depression opens the doors for better understanding and awareness which will allow your regulars to make sure the mood in the room stays normal, even if you might be going through a very rough time at that moment.
4. Stay consistent. One of the things my EX did very well for the last year she was on cam was her consistency. She chose to cam every Monday, Thursday, Friday and Sunday for 2 hours. Keeping that consistent schedule not only held her accountable but allowed her viewers to know when she would need the most support.
5. Take "me" time. It is very important to make sure that you get "me" time. Do something that makes you happy, such as writing, reading, walking outside, taking a nap, staring at an extremely bright light, and so on. Reset your emotions and relax.