In my younger days - nothing bothered me. Then I had 'that job', like many in the comments have talked about. Stress to the max. It took me to some dark, dark places.

Eventually - I just said "this isn't worth my life" and quit. Just up and walked out. I vowed never again would I let a job have that affect on me.

I've lived from then on with that as my mantra, although lately - stress is creeping back in at my current place.