I've had problems with trying to survive past day 15 due to mental health. Walks don't let me regenerate because I get hungry and when I get hungry; I eat the vegetables and they drain my mental health again.  Even sleeping drains it.

How do I improve my mental health and keep it up?

I'm quite curious. I've not had this problem at all, I basically only was eating vegetables and was having no problems with sanity until I started passing out from lack of paying attention to the tired bar.