As noted earlier, clinical depression will screw you over no matter what choices you make intellectually. It's something a professional needs to evaluate. It's worth doing, if you haven't. I had something that resembled depression, but was actually an endocrine issue that killed my energy and made tasks that were easy before/after it was addressed seem like massive undertakings. It's a lot easier to overcome "laziness" when your body functions properly, and I speak from first hand experience!
Similarly, depression can have physiological sources which you can't will away, and the best/only *good* way to make sure you don't have something like this screwing with your life is to have someone who knows what they're doing go through the process of evaluating it. It's no different from checking for cancer, having an ortho specialist look at a joint injury, or having a dentist fill a cavity as a matter of process. Those are also things that individuals can't do themselves...in some cases even if they're trained in the field they still need someone else.
Even so, it's best to have professionals evaluate what's real, along with the person in question evaluating the process to see if it's helping. People really do have physiological causes/problems, but it's not always so, or not always the sole cause of discomfort/unhappiness/etc. When it comes to some medical conditions, you're also stuck with a nasty reality of making a tradeoff between being a "functional X" vs the side effects of the medication for that condition. Those side effects can be brutal too, to the point where it's not clear which is the better answer. That's something the patient has to decide.
Aside from the medical stuff, there's no objective meaning in life, best I can tell. Nobody can define another person's utility function for them, so to speak. There's not even a realistic way to know if our own choices optimized our own happiness, because those shape us too and it's hard to say what would have happened given other paths. There are a few general pieces of advice I can give:
- Maybe there are things in reach, once identified. Basically, what is a "worthwhile" life? That answer will look different for each person, but to the extent that it bothers you, this shouldn't be something ill-defined. Answer that by defining objective, observable world state in which your life is "worthwhile". If you want to play in the NFL as a 30 year old woman, you're probably screwed. But that's probably not what the world state envisioned will look like.
- I recommend strongly against depending on external validation as a primary source of self worth. It's a path of destruction. Yes, we live with other people and depend on each other, to varying degrees. Those connections are important. But this aspect of validation should come from within.
- Do not think mind can overcome matter in a literal sense. The brain is a finite organ, like any other. Nobody has infinite willpower, and even the most happy and successful people don't have comic book superpowers; their minds will go to a dark place as surely as anybody else if subjected to enough damage or trauma. You, me, anybody, no exceptions. If you have a chemical imbalance, you can no more will that away than you can will yourself to leg press an entire building or regenerate a limb. It's not a thing the human body can do. But there ARE things that can be done, to at least help.