I've been in an on-and-off existential funk for most of the last two years. At times I've seriously wondered if I was capital-D Depressed. I don't think I was though - as in, my problem was caused by a specific frustration with things wrong with my life, rather than a chemical imbalance in my brain.

To clarify: when people feel "anxious and depressed for no discernible reason", it might be because of a neurological disorder in their brain. Even happy times feel empty and meaningless. Or, it might be because of an actual issue in their lives, but one they haven't fully discerned. It's hard to tell which group you might be in.

At the time I found doing volunteering did give me some genuine happiness. Another activity I found very meaningful was deep reading of philosophy and literature. Over time the reading became less and less rewarding though (the volunteering stopped because of logistical issues). I had a feeling that there was some process that was sucking meaning out of everything good in my life, which was pretty scary, and made me wonder if I was developing clinical depression.

In my case, I've come to the conclusion that my unhappiness was caused by unacknowledged issues with my life situation, not neurochemistry. You mention "I had all of my dreams in life shattered" - my situation was not so drastic, but still a bit similar. I'd been reading about startups all throughout university, and was accepted into a prestigious new accelerator on graduating (more of a pre-accelerator, actually, so ideas and teams were in a bit of flux). It was intense but I felt on top of the world. My problem was I "pivoted" three times while looking for the right team + idea, until the accelerator programme had ended and I had no serious traction with anything. So I found myself working in Starbucks on crappy PHP code for a freelance client. Then that dried up and I found another short-term gig basically doing monkey work with Excel. I went through a hairy few weeks after a late invoice where I almost ran out of cash. So I was trying to figure out my life direction while also struggling to survive.

Looking back, I had a combination of a) over-ambition ("I need to be working on a potentially huge startup before I turn 24") and b) lack of understanding of the effort required to create something halfway-decent (and the experience required to create something actually good).

Over time I managed to tune down the over-ambition through a combination of introspection, CBT, self-acceptance and observation of how difficult even very smart people have obtaining moderate success. The work ethic I improved by taking a couple of standard web development jobs and learning to do things the right way. Still, this existential depression has waxed and waned over the last two years, and (I now believe) it's because at least part of my psyche never stopped believing that I could and should be doing something greater.

It's like - as we grow up we get used to the fact that our younger dreams often aren't worth sticking to. Lots of people wanted to be astronauts as kids, but they probably don't despair that they never became astronauts, just because it's such an unlikely thing to become. But the minor character in Fight Club who secretly wanted to become a veterinarian - well, it was a challenge to become a veterinarian but not an impossible challenge, so why didn't he do it?

So my small suggestion to you is: take a look at your "shattered dreams" and rationally evaluate which still seem achievable and worthwhile.

Avoid the twin emotional traps of grandiosity and helplessness ("yes, this is the idea, I'm going to work on becoming the next Elon Musk for 18 hours a day and get VC money and Techcrunch coverage and everyone will love me forever" vs "why do I want to work on a new project, just summoning up the effort will add more strife to my existence in the valley of tears, I should just find a safe spot and stop moving"). A good perspective is one of balance, clarity and equanimity: "my life is OK, there are things that I can improve and I will patiently work on plans to improve them, and try and build relationships with people who I can help or who can help me".