I have SAD. It's a form of depression which is triggered by lower light levels in Winter. I've suffered from it since the age of 14, though I was in such a terrible place at the time that I didn't work out the pattern behind it until about 3 years later.
For me, depression is nothing so simple as feeling sad all the time. It's a profound apathy; I was unable to care about anything that I should care about, from my own health to work to the future. For the longest time, I both cursed my condition - knowing that approximately half the year I wouldn't have any energy or motivation to do anything useful took it's toll even in the Summer, knowing it was looming on the horizon - and resigned to it - it was inevitably going to happen, so I'd better just settle in and wait it out.
I got incredibly low, not able to find the energy to feed myself properly, or shower. I had lots of troubles getting to sleep, and when I did, I slept for longer and longer stretches of time. And nothing seemed to rest me. An that's when the secondary symptoms set in - you feel so worthless unable to even take care of yourself, and you put yourself down. Everyone else can manage these basic things, why can't you? I started feeling guilty about not being able to do work, and couldn't distract myself with enjoyable things because they held no interest for me. Even turning on the television or picking up a book seemed like too much effort. Existing seemed like too much effort, to be honest. I also felt guilty for being depressed. I had a roof over my head, a supportive and loving family, I was lucky enough to get into and afford a university I wanted...but that's the thing. Depression isn't 'being sad'. It doesn't matter if you have things to be happy about - it'll strike regardless.
Anyway, that's the bad part. The good part is, I survived and made it through, and this has been my best winter for years. For a few different reasons. One, I have a small but caring support network. They kept checking in, reminding me of the good, reminding me that this was all temporary and I'd get through it. Second, every time I felt guilty about 'not being good enough' to deal with it, I reminded myself that this isn't laziness. It's a chemical imbalance in your brain. You wouldn't put down an amputee for not taking the stairs, would you? It's a physical condition that can't be seen. Like heart conditions, diabetes, etc. You need to acknowledge that you are ill, and you do need help, just like you would with any other illness. Third - this year I started actively managing my condition before it got too bad. I got the cheapest lightbox I could off amazon, and started using it every morning in the autumn before my symptoms started. I took St Johns Wort, again, before the symptoms began. And this winter, I've been fine. I know this won't work for everyone, and there are side effects to consider, but for me, it's balanced me out perfectly.
I'll add some links to the bottom of this post. If you think you might be suffering from this or any other kind of depression, please, get help. It can affect anyone, of any age, gender, creed, colour, sexuality or upbringing. And it can be managed.
Please feel free to ask any questions - one of the worst things about depression is the lack of information as the feeling of isolation it can bring. Please don't suffer silently; if you think you might have it, or a friend or family member might, reach out to people. You would be surprise how common it really is.
Lightbox:
http://www.amazon.co.uk/Lifemax-Light-107a-Simulated-Daylight/dp/B002MRS5OW/ref=sr_1_3?ie=UTF8&qid=1427151210&sr=8-3&keywords=sad+lamp More information on St Johns Wort:
http://www.mind.org.uk/information-support/drugs-and-treatments/st-johns-wort/#.VRCZzWYzSX0
