This is for all the people who have experience about depression. 

So my friend has depression and it's currently quite bad. I understand that it's not his fault and that it affects his life. I have done quite a bit of research from the net but it never tells me how it's really like on a personal level, and of course everyone is different. Sometimes I don't understand the things he does (or doesn't do) because of his depression. 

Is it even possible for me to understand depression as I don't have it?