I regret switching my tribe to X2 speed and then going to sleep, thinking I had paused the game. Fortunately, I checked on the tribe the next morning so it wasn't too bad, but it messed up my Esteemed Elders and Breeding programs! I had to work extra hard to make up for it.
I still use X2 at times, but now I double check that the game is actually paused when I want it paused.
ERR...breeding progam? And here I thought was the only crazy one who did that...!
As for regrets, I regret not breeding one of my favorite females before she became elderly! So, speaking of breeding programs, it messed mine up