The job market is dismal right now. In the 90s I had retailers calling me at home WITHOUT me ever putting in an application, asking if I'd like to work part-time because a friend of a friend said I used to do that. Today, those same jobs have triple interviews, tests, and, as you say, 50 people for every opening.
It took me nearly two years of sending out app after app and going to about six interviews to get my current minimum wage retail job. I was hired as a temporary Christmas worker and they kept me on. Mid-October was my one year anniversary there. I still make terrible low pay but it's something.
I know exactly how you feel. It's SO hard not to take it personally, but honestly, it is NOT personal. The economy is just horrible, that's all.
Maybe a short break from applying would be good for you. If you can, take a week or two off and just be good to yourself. Try to reach out to other unemployed people for emotional support and references. Do you have a hobby? The reason I ask is that if you are doing something you love a bit each day, it makes it easier. It isn't paid, but it helps you feel better.
Hang in there. You are not useless, just unemployed during very tough times.