Fortunately, I have never experienced the condition but I would assume the first logical step is to determine if your psychological state is in fact "Depression" as defined by a medical professional, and then take necessary or prescribed actions to minimize or hopefully eliminate the potential energy draining symptoms. A self diagnosis is probably not the prudent route to take when trying to pin point the exact root cause of the ailment if in fact a precise "Trigger" can indeed be identified.
Is it "Depression" which can be all consuming or even physically and mentally debilitating, or, is it a significantly milder case of the "Blues" or even just a brief bout with "Loneliness"? Both of which can usually be conquered with a little help from friends and family combined with the simple passage of time.
Proper analysis and conclusions can only be performed and rendered by a highly qualified and licensed psychologist or psychiatrist. In addition, if an anti depressant is prescribed, always proceed with caution by reading the instructions in full to uncover any and all possible side effects.