I am not entirely sure how this is going to work now, but the idea of "diminishing returns" can be added to stealing of energy.
For example:
First fight: 3 x multiplier. (i.e. 3 times as much as you win now)
Fight two: 1.5 x
Fight three: 0.75 x
..
Fight n: 3 / (2^(n-1))
At the end of the day, it gets reset.