What does "darker counsel" mean here?

"The mentally ill should cling to darker counsel. They should not underestimate the persecutory aspects of optimism."

Question

What does "darker counsel" mean here?

"The mentally ill should cling to darker counsel. They should not underestimate the persecutory aspects of optimism."

Answer

It is sarcasm. It is terrible advice. The mentally ill need to do the exact opposite: cling to optimism, ignore darker voices.

Answer

It refers to the therapeutic effect of confronting & solving your deep dark buried problems, instead of ignoring them and being ignorantly optimistic.