You are really beating yourself up about this, your sense of self worth was non-existant and it helped contribute to your unraveling. I can definitely see some resemblesances to our stories, although instead of letting her go, I just dragged her through the mud and subconsciously wanted her to know that I was unworthy. Purposely not doing things she told me she wanted as a point. And with my lifestyle and priorities, I was unworthy. Even this past weekend, I still proved to her I was unworthy with my boorish behavior and totally unreflective of my progress. But it comes to a time when if you felt you were lagging in the relationship, and she cares about you and wants to make it work still, that you either fight or flight. And you ran. Abandoned ship. Took for granted that she would still be there for a year after not seeing you for a while. Not to say you didn't try, but when you don't have them in person, most of the intimacy needs can't be met. My ex went all summer away from school and then when she got back to school with her friends again and met a bunch of new guys, I got less than a month before I got the boot.
But yeah, what has happened has happened. You cannot change how you gotten here, and all the panic things you did to try and take advantage of how she felt before. It's a brutal lesson that life dishes out to you. You probably think "Why couldn't it work out like those couples you see that go through hell and everything together and are still together today?" Truth is those relationships are rarely happy, most stay in them for comfort when they are slowly dying inside. It's totally unrealistic, and we all make mistakes that usually cost us our relationships. The most important part of this is to not let this experience go to waste. Use this as the motivation to make YOU a better person. You know you were a bum and had no job, no education, no future. So now's your chance (if you haven't already). I think a part of you knows that even so, it will never bring her back and your chances of running into her again are slim to none. And it's the truth. But as they say, there are plenty of people in this world for you, and the more motivated and prepared you make yourself now, the more likely you will be ready for that person when they come along. You weren't prepared this time, so be ready the next time.
People like your ex don't just come along every day though, and it's difficult being alone after having the sense of somebody being there for this long a time. You find a way to deal. Before this weekend, I've had zero intimacy for probably around eight months, and the intimacy I had this weekend was just a hook up. Doesn't exactly make you feel like a whole person afterwards, but it is what it is. You find a way to deal, you get used to it, you are numb, etc. But we all find a way to deal, and sulking about it isn't a very good way to do it. Time will make things better and if you are proactive with your time, you can make the most of it and honestly feel some of the self worth that you weren't before.
I wish I had a magic fix it button that you could press that could change everything back to how you want it. But there isn't. You are young, it isn't the end of the world. Life moves on, as does every single person who has gone through a break up like you. As you said, our problems seem to consume us while to everybody else it's trivial. Just like their break ups are trivial to you. You will listen but ultimately it's they who have to pull themself out of it. It's you who has to pull yourself out of this break up as a new, better person.
Waking up next to a beautiful girl,
Step outside and say hello to my beautiful world.