When I was young, 22 in fact (I am 54 now) I was finally diagnosed with depression. After some weeks of charting my mood so we could see what was happening, we discovered I had a two-week cycle- I spent a day or two falling into the trough of depression where I would stay for 2 weeks. I would then spend a day or two coming back UP to "normal", which, mood-wise, is a little bit lower than a "normal" person's bummed-out day.
So- BiPolar disorder. My "manic/up phase" is still less than what a non-sufferer would feel and only lasts 2 weeks. The trough sucks badly... loss of interest, energy, joy, etc. Have to FIGHT to not just sit in a corner and... sit.
Luckily, I've had 30 years of experience dealing with this so no fear... just have to handle the depression for two weeks and everything will be fine!
For two weeks :)