You have to choose the bounty that has a good and reliable manager. If you are feeling depressed that your efforts were wasted that's the other side of bounties.
If they aren't able to reach their soft/hard cap they will never pay your efforts so if you want to get paid with the bounty you are joining. Just choose the bounty that has an experienced bounty manager and assures the participants to get paid.
I agree, if you are gonna join or participate in bounty campaign, you should prepare yourself for the worst. I know its frustrating and depressing but in life there will be always a time that there will be some hard times or your efforts didn't gave you a good result, but as long as life goes on just keep on doing it and at the same time be careful on what campaign you will join to and study it first before making any move.
it is true, we must prepare mentally to accept some risk that will come because in cryptocurrency have big risk without exception join bounty campaign, just think as learning to trigger the spirit forward, I have several times following bounty and ended unpaid but we only need sincere because surely there will be instead.