You are really young, and I say that as a really young person too (22). At 18, you're probably still living with your parents or you just got out of here. You're still a student, maybe working aside of your study but you haven't entered the work force yet. And here you are, putting this ENORMOUS pressure on yourself. Relax! You're not even halfway through life and I know it feels like you are expected to be so much more, but you're not even an adult yet.
Also, really big kudos for wanting to improve. That is a huge step and no matter what will happen in the next 5, 10 years, I know you will accomplish what you set your mind to because you clearly have this drive. It's admirable!
I started working on my discipline when I was 18 too, and I got my ups and downs (more downs, actually) but 4 years later, I'm starting to get exactly where I wanted to be. And it's going faster and faster. At school, learning goes fast: new chapter, a few months later, a test and then this part is done. In real life, learning is sloooow and curvy and really weird. You need to realize this. So learning discipline will be slow, so slow that you will feel like you are making no progress. And then BAM, you reach the next level, you pile on success... and it starts to feel slow again. It's a cycle and you'll get used to it. The key is to not give up when things start to get slow, when you see no progress (or even regression). Forget what you know about learning from school, learning in any other setting look more like what I just described.
Also, as you get older and pile some actual experience, discipline will come more naturally (at least that was my experience). You get tired of doing nothing all day, not cleaning, not making any progress anywhere so you start working on something. For a period of months you'll see progress then it slows so the first few times you'll stop for a long time. And you get tired of fucking around again. So you start working again... but this time it's easier. You do that a few time, experience life and the challenges it throws at you and then one day, you stop wanting to stop, you just keep going. It's a whole shift in mindset that happens slowly as you take action.
So start experimenting how you can be a better version of yourself. Some things will work, some won't. But above all, trust the process. Trust that all the victories (however small) AND all the failures (however big) will get you where you want to be. Know that it will take time, so enjoying even the smallest victories but most importantly the process is key to be happy and keep going.
Another important point that I want to make: stop being so negative about yourself. It is really important, because why would you want to help someone you hate ? Why hate yourself in the first place ? Yeah you fucked up a few times, big deal. It happens, all the time, to everyone. Just forgive your past self and remember the lesson past you taught you: don't do that thing again, it's bad (it's actually valuable! Very very valuable). And don't fall into the trap of thinking "I can't love myself now, I need to get better first". Nah, love yourself first, get better as an act of love. I know it sounds super weird and if you're anything like I was, loving yourself is gonna be the toughest challenge of your life. But it's important and it's gonna make all area of your life a whole better.
Every time you think of something negative about yourself, think of something positive as well (even something super small like "hey I helped my dad with the dishes yesterday! That's kinda cool :3"). Help people. Dishes, cleaning, compliment someone. It will remind you that you are valuable, that you matter in this world. Sometimes it's hard to see that we do matter (because you know, you realize that there's 7 billion people and that's a huge number) but every single human being matters. You talked about that guardian spirit you wish existed... well why not be your guardian spirit ? Always having a kind word for yourself, giving you a gentle push and encouraging you on the difficult times. That's actually what I do now, and my life goes much smoother.
Okay that rambling went on long enough. Sorry if that was too long or difficult to read (also not a native english speaker, I did my best with grammar and spelling). I really hope this helped you though, and I wish you the best!