Its truly amazing how one can go from stable to chaos in such a short time.
My Kingdom of Scotland was doing fine until my king died. Both my male heirs had died so a decade before I married someone and had a male son. So he inherited at age 10.

The entire kingdom revolted save for a few counties. At first it was just one vassal. I held him off with the help of mercs. Then another revolted. Then England attacked, claiming all of Scotland. I had no forces left and all my cities were under siege, so I surrendered Scotland. I only had Ireland left. Then a vassals claimed Ireland, and she had 3,000 soldiers and I had none. So I let her become my new liege. Now I am the duke of roughly half of Ireland. I was able to put down a smaller revolt by one of my vassals but its rough.

Amazing how I went from rags to riches in roughly 3 years.