Hey there!
Recognizing that a failed business is bothering you is really important- if that business was something you put a lot of time and energy into, you may actually be mourning it's loss, so give yourself the time and space to do that.
I suffered from depression since I was about 8 years old, until I was around 22- at that point, I found that my depression stemmed from anxiety, and even now, when my anxiety becomes unmanageable, I still slip into depression as a "safety feature." It's not a great fallback, but at least I know what I'm doing when I'm depressed. (I realize that sounds pretty sad, but it's a part of life for me, so I'm not overly sad about it)
I also dealt with my depression without medication, and I even continue to deal with my anxiety without medication. It's not an easy road, and for a very long time, I kept being told that I should have medication... and that I was "not taking my depression seriously" by refusing their suggestions of medication, and only medication. I generally couldn't get the help I needed, so I had to find my own way.
So, first off, I'm going to tell you something that one of my best, and most brief, counsellors told me: What if you just had it over to visit, and let it stay, instead of fighting it?
The emotion will be here whether you like it or not, and... you're still around! So, why not let yourself be depressed instead of constantly fighting it? Just relax, and it'll move on in it's time.
I realize that can be scary. There are a lot of questions that come up when it's suggested. Things like "What if it just gets worse?" (It won't, it never got worse unless I actually fought it), "What if it never goes away?" (You can't have one emotional state for too long, it's impossible, so it WILL move on), and finally "If I don't fight it, wouldn't I be just giving up?" (No, you are trying a new method of dealing with it, of managing it).
You are allowed to have emotions, including feeling depressed! It's okay.
The second part is the habits of depression. Because I was like this for so long, and very much during some key parts of my life, I formed a lot of behaviours that related to depression. They seemed to perpetuate my depression, long after I had realized I no longer needed it to "protect" me, or had a use for it at all. I had to start changing, and I had to know about those behaviours before I could shift them, or get rid of them.
For me, it was a lot of self-talk, and a lot of particular actions. I stopped participating in the News almost entirely- no news websites, no TV, no newspaper, none of that. It depressed me, made me afraid of the world, and sad. Not great.
And with self talk... well, things like "I can't do that," or "I'm not good enough," though they aren't really put into words like that. It was a feeling that I was inadequate, less-than-human, that I was lower and lesser than everyone around me. That somehow I, some lowly horrible being that I believed I was, had been confused for being just like everyone else... and they would eventually figure out I wasn't the same.
You know what? I am the same. I am human, and I am just as capable. I may also be "different" in that I am not the normal for most people: My progress physically can be quite slow, and my progress mentally can sometimes have holes in it that other people do not have. But, I am also a writer, I am someone who sees through people's egos and disguises, I see their behaviours and their motivations. There are things I pick up that other people do not. In that way, I am "different," but it's something I'm proud of.
My suggestion right now... try not to push yourself too hard. Go for a walk, even for ten minutes, every day. Make a habit of it.
Perhaps start a journal, start conversations with yourself. You're a person who needs someone to talk to, and who better than you to do that? You may already know what you're going to say, but it's the act of saying it that is important. It's the act of listening to yourself, that is important.
Try some meditation if you like, too. Depression can be distracting and difficult, and for me, anxiety is similar- distracting, busy. I like meditation as a way of gaining some perspective, allowing myself to see more than just a mental illness.
Just go slow. Trust yourself. :)
(And, yes, when you need help, PLEASE call someone. Those hotlines are there for YOU, and they can be super useful. Your self-care is important, and sometimes that means bringing someone else in.)