It's OK. So yeah if you decided to be a professional concept artist in 7 years, you indeed failed. But how are you so sure 7 years is the maximum amount of time you can take for this? And how is it exactly failure? In these 7 years you acheived several things, maybe not your big dream but you managed to inspire other people (me for example), you improved in drawing and maybe you also acheived things in your personal life that we do not know about.
Also if you want to be a concept artist you just have to create concept art. That is something you can do. I have seen it on DeviantART and in this sketchbook. The only difference is that some people get paid for it and some less or not. You should also decide for yourself what you want with your artwork. Do you want a game with your superdark artwork and what-not? Look for ways to make it yourself. Or do you want to make sick illustrations? Then make that. If there is no motivation, try to do the things that do motivate you. I hope this is some good advice for you. I have had these dark times as well where I just wanted to give up. You and other people posted in my sketchbook to cheer me on. I guess I have to return the favor now.
You might feel that your journey is pointless currently but I think it is brave to keep trying. Even when the odds are not in your favor. At least you can say you tried, that you went out there, that you aimed for something better. It takes great courage to keep doing that in the adult world where you have to have a job and a mortgage.