I've created a throwaway account to post this .
I just need to say how empty I feel to anyone who might listen. I'm a married father, with a lot to be thankful for, but most of my waking life is spent somewhere between feeling depressed and abject misery.
I made a terrible career decision in the midst of a bad depressive episode in a misguided effort to stop myself feeling so terrible and actively contemplating suicide, and many years later have come to realise that my actions have ruined any chance I have of happiness. I've ended up in a career that I'm no good at and I very much dislike, which only appears to hold a lifetime of stress and low wages for the effort it involves, and my past career history does not lend itself to moving into a different path (I'm currently a specialised professional in the British public sector). I spend my days seeing my contemporaries who made better choices living a life I thought I was going to have, and feeling despair at how trapped I feel. 
Ive lost any confidence I ever had, and having 2 kids and a wife who's job would not be enough to secure a decent future for any of us alone makes me feel that making a radical change like retraining is impossible due to the likely debt I woul incur, and my own ability to succeed at anything else. I feel like I'm too old to have a reasonable career if I start again (38), and I seem to lack the ability to find ways of getting into other work. 
I vasilate between panicking about my current situation, hitting the depths when contemplating a miserable future, helplessly seeking a way out, and becoming furious at myself for my disastrous choices.
I feel like I've let down everyone in my life, and am going to let down my kids because I can't give them what they need to have a better life than me financially or in social capital. 
All I want to do is sleep. I think about quitting and trying to get a low stress, low responsibility job that I can't mess up, but even that seems beyond me and would only make my kids futures worse 
I've been told I'm depressed, but to me that is just a description of my reaction to a ruined life; I've tried medication, therapy and other beneficial activities, but as the underlying problems are there, I can't see how they can help. I've asked my family, my wife and the few friends I have if they can help me think my way out of my situation, but no one can help me and after all this time I think I've burned out their desire to try. And I realise it's not their responsibility to help me. I've had professional careers counseling, but I found it unhelpful as it seems aimed at people who gave the capability of being able to make good decisions - I am useless and bereft of ideas.
I often wish I would die; I'm too much of a coward to kill myself, but I think a lot about dying in accidents or of illness. I don't enjoy life anymore and the future looks terrible.
I just want to cry, and to be taken care of, which is pathetic. My younger self would not recognise what I've become and I'm ashamed.
Thanks for listening.