Why can't I do anything right?

I was doing better at work, and then I undid all my progress with one stupid, careless mistake. Now my boss thinks I'm blowing off my job because of my summer practicum.

Why do I keep doing this? Do I subconsciously want to be an inconsiderate f***-up? Maybe they're right that I secretly want to get fired because I get some kind of sick enjoyment from making things difficult for others. Anyone else would have learned to stop being a f***-up, but I keep making the same mistakes over and over.

I feel like I need a severe punishment, because it's the only thing that will force me to behave correctly.

Instead of punishment, have you considered therapy? I find it very helpful. It can get at any underlying motives you might have, plus help to relieve stress, which can lead to making mistakes.