Having personal experience on the subjet - depression- I'd just like to clear a few things up so you understand.

Depression is an illness.

Depression is a mental ailment that may make one think negatively,may make one feel constantly lethargic, cause lack of sleep, thoughts of suicide, over/under eating. One may suddenly feel sad for no reason, lose enjoyment of what used to be enjoyable to them. One may become more apathetic, and withdrawn from others.

One can not just 'snap out' of depression.

It's not just one of those 'feeling-down' moods. It takes treatments to recover and minimize the symptoms. These treatments won't work overnight, either. The site link below provides more information on treatments.

http://www.psychologyinfo.com/depression/treatment.htm

Someone who is depressed should just get over it, and if they don't, they're weak.

As I just said, depression is an illness. You can't just 'get over' it. They are not weak, they just need treatments to help them. They may not recognize the symptoms of depression, or might be afraid that others may call them 'weak'.

The following is a good site to go to learn more on depression.

http://www.psychologyinfo.com/depression/index.html