The question isn't about school vs. real life - this IS your real life.
No matter what job you do, you're going to do the same things, over and over again. You never just hand them in once and leave forget about it forever. Don't think of assignments as things you hand in and forget about. Think of them as things you practice, and corrections are rehearsal and more practice. You wouldn't go on the ice for the first time an hour before an Olympic hockey game, expect to win, and then walk away. Learning to Learn, Learning to Think, Learning to Communicate are hard-core brain sports. And this? This is just the warm up.
Marks are just numbers - they don't put a value on who you are, on what you can do. People will judge you by your marks, even though they shouldn't. It's up to you to choose what information you'll give them to judge you on. But never forget the numbers aren't YOU.
The real question will always be - How Effectively Do You Learn? What you learn will depend on your job and on your interests and on your needs. If you know how to learn effectively, life will be much easier. If you don't know how to learn, and how you learn best, you're going to have to rely on others and hope they're not scamming you. Is that a risk you want to take for the rest of your life?
Call it a process, call it a journey, call it whatever you like - it's going to keep coming at you. The work will never be done, there will always be more to do - more cleaning, more dishes, more writing, more things to fix or reports to prepare. THAT is the real reason to set short term goals - like rest stops on a long road trip, they keep you refreshed enough to keep going.
What you do or don't do for a living will not automatically make you better or worse than anyone else. Money won't make you a better or even a happier person - just a wealthier one. Decide what's most important to you, make the choices you need to in order to go after it, and accept the fact that you won't have it all.
You will change. It's allowed. Enjoy it. Do the best you can, here and now, and don't worry about it if your best is more or less or just different tomorrow or a year from now than it was today. Let your dreams and goals adapt as you grown and change, or you'll strangle yourself on missed opportunities and unrealistic expectations.
Debt is painful. Avoid it as much as you can, and pay it off as quick as you can. Period.
You may be tired of trying, but your brain isn't. Your physical brain actually feeds you its very-own-self-created-feel-great-chemicals in that space between "maybe I can do this...but maybe I'll face plant..." in the moments before you either succeed or fail. If you just don't try, if you just settle, your brain feeds itself self-created-downer-chemicals. Even if you don't succeed at every effort, by not trying you cut yourself off from some powerful woohoo feelings.
THERE IS NOTHING WRONG WITH FAILING AT A TASK. Seriously. When you were little and learning to walk, you fell down. A lot. And it hurt. You probably hit your head or face planted a few times. People laughed at you. And you got back up, and you tried again. The world didn't end. You can get around. You can probably run, or jog, maybe even dance, or jump hurdles, or you can roll, or move in some way. If you're really talented, you might be able to walk, talk and chew gum at the same time. The point is that you have failed, over and over and over again, and you didn't quit. You weren't born knowing how to walk. You weren't born knowing much, really. You need to learn almost everything - and almost everything you learn will involve effort, and failure and possibly some pain. And it's worth it. I promise it'll never be the end of the world. Feel free to fail. Then get back up and take another kick at it. Again. Again. And again. As often as you need to. Take breaks when you need to, to respect your own sense of "um, not right now". If anyone gives you a hard time, ask them how many times they fell down while learning to walk. While they're counting those failures up, you'll have another chance to try again.