That's a shame. There's nothing about that in the rules. And if you also leave the game on XL+U because you're losing to some overpowered opponent...
I just didn't feel like playing, so I left. I shouldn't have started in the first place, I agree. But the overpowered opponent was just an excuse, because saving and wasting time wasn't really appealing to me.
The hardest battles are fought in the mind