We recently came to realize the metagame relies a little too much on random rolls, which can sometimes result in bad experience. This will be addressed in version 0.14. However, a common mistake some players do is expanding quickly without stabilizing the fiefdoms they recently conquered.
Before attacking another fiefdom, I'd recommend ensuring the following;
1. High Morale (~20) in all your fiefdoms
2. High Obedience () in all your fiefdoms
3. Fully built (or close to) fiefdoms
4. About 100+ gold in your treasury to use Shadow Institute operations after the war and easily control your Obedience/Morale