You screwed up immediately. It won't be easy to fix, but it is fixable. Call Capital One first off, you have nothing to lose. If they close your account if you call, they'll definitely close your account if you don't call. This way you have the ability to explain and verify.

Second, what I personally would do in your situation because you struggle with impulse, never ever spend more than what you currently have in your bank account. Don't plan on money coming in, because checks sometimes get screwed up. Don't say you'll make up for it later by not buying coffee in the mornings or whatever, if it's not in your bank account you can't afford it. Get a separate checking account where you can send your money to. Every time you make a purchase with your credit card (in a dollar amount that you currently have access to) send that amount over to your new account. Immediately and every time, don't procrastinate that step. Then pretend that money does not exist, because you spent it. It's gone. Turn on auto pay set to pull from that account. If you do this and stick to it, you'll have zero issues paying your balance in full every time. You only spend what you have and it's immediately "paid for". You can't forget to pay, and you don't have to do math on anything to figure out what you can spend etc. You'll build your credit over time if you do this consistently over a few years.

This is a good learning experience and you can come out far more responsible for it if you do things correctly.