I also had a HELLISH day trying to get through my water quest yesterday. One trick I have found is that when you get stuck you can "slow down" -- that is, try just doing one battle every 15 - 30 minutes, because sometimes the difficulty level varies based on the time zones of the people you are playing. You can also join a daily tournament and alternate "ranked (quest)" battles with tournament battles (again, every 15 - 30 minutes). This has worked for me quite a few times...