Am I a fool for walking away from a job with a pension?

A little background- I live in Canada, I'm in my early 40's, and I have been working in the public sector for 21 years. I am about 12 years away from receiving a full pension. The problem...the job is sucking the life out of me.

I want to find something new, but I wonder if I am just foolish to walk away from the proverbial "golden handcuffs."

I am unsure if I'll be able to find another job that can turn into a career that would:
A) pay me close to what I was making, and
B) even consider me for the job since I'm over 40.

I think life's too short to do something you are no longer passionate about. Although, the grass isn't always greener on the other side. I also don't want to make a wrong decision that will impact my future and retirement.

I'm so torn on what to do. Does anyone have any suggestions/advice?

Thanks in advance.