ok, so many players hate the side effects of upgrading your energy tank. To the point where, most don't even bother upgrading. A major reason for this (although not the only reason) is mood which increases at a 1:1 level with energy. So I propose that instead of Mood increasing linearly its instead increases with diminishing returns.
So for example, the first +10 energy tank you buy you will increase your mood by 10 but by the time you get to 1000 energy your mood may increase by 1/10th of the energy upgrade. With lower and lower results.
So while it will still be more difficult to keep your mood at 90%+ it will be far far easier then the current system and hopefully players with no longer feel disadvantaged by increasing there energy levels.
TL/DR: Mood shouldn't increase at a 1:1 ratio with energy. Instead it should have diminishing returns.