Well it's seasonal, so the only way to resolve it would be to move to an area with a lot of sunlight/no winter. Which I don't think would be realistically possible - I can't imagine the military would deploy me to only warm or tropical areas when, for instance, their operational needs are elsewhere.
However, I'm still able to function without St. John's Wort (I've only started taking them two years ago despite it affecting me for as long as I can remember). The difference is I'd feel more negative emotions/have a negative mindset, and to an extent more aggressive/willing to fight (which might be good in a combat situation, though I can also imagine how it might be counterproductive).