At the end of my first I had the same miserable and pissed-off ALL the time feelings. It was at 13 years.I went 24.5 years in my first. One day I realised just how miserable and pissed-off I was every single @#$& day and for a change I snapped back and yelled at her. My first time every getting that angry with her. I realised right then that it couldn't go on, there were numerous problems and dark thoughts were on my mind far too often.
Not sure what your dark thoughts were.
I didn't talk about this for years but the older I get it has become therapeutic. My ex and my then 4 year old daughter went shopping one Saturday morning. I sat on the floor by the bed with my S&W .38 Special in hand. In the end the thing that kept me from using it was the fear that my daughter would be the first in the room. So instead I went to the garage and got a couple lawn trash bags and started packing my stuff.