I believe this to an extent. Poor mental health can have a negative effect on your physical health and can delay ovulation. I believe that thoughts are energy and its very important that the energy you put out in positive if you want to achieve positive results.
However, as a student midwife, I see many many women who are pregnant and have mental health issues. It's very common. I can't remember the exact source, but I'm pretty sure I read an article recently that said current evidence shows that whilst stress can affect ovulation, if you do ovulate, your chances of getting pregnant are the same as everyone else's.