optimistaken 

To be optimistaken is to be optimistic and mistaken about something at the same time.

Engineers are often optimistaken about their schedules.

optimistaken by swerdna May 21, 2017

Optimistamania 

Excessive excitement or enthusiasm, craze for an optimist or optimistic person or to have mania for optimism.

I've come down with a severe case of optimistamania and I love it!

Optimistamania by Mistymeanor February 20, 2011

optimistake 

A situation that goes wrong due to your mistakes because you expressed way too much optimism than it deserved.

I sense that this deal could go wrong with our optimistake behavior, let's be careful.

optimistake by sgrbn May 28, 2018