I swear to god, you are a carbon copy of my boyfriend. I swear. I swear! Am I in a parallel universe? Seriously. This is blowing my mind.

Even the time period's you're talking about are on the dot, it's freaky.
Anyway, it was interesting to see the responses to what would be my boyfriend's perspective, being that I'm in the same position your girlfriend is in. Let me go ahead and say how frustrating it is trying to be serious with someone who's picking up the pieces. The thing you gotta remember is that girls equate progress with love sometimes, and if she see's you slipping into old habits, she's going to think you just don't care about yourself or the relationship. And maybe she's right. Maybe there are days you just don't care, as much as you want to. But you gotta take some initiative and not show how easily beaten you are, otherwise she's gonna think you don't plan on changing if youre going back into old habits.
Dude I'm really trying to not lecture you like you're him right now, haha.
Straight up though, it takes work. It's cool you're reaching out to other people for advice, it speaks volumes about how much you care. That's the bets way to do it really since you just CAN'T make such marked changes on your own. You're off to a good start, although you may need more guidance than that. I would honestly buy a self help book or something to start. If thats not your style, what I usually do is try to research forms of philosophy or even religion [I'm not religious but Buddhists and Jews hold a place in my heart] or things such as that to sort of develop a mindset that would help me perceive the world better so the rest falls into place. [Just don't touch Nihilism, you'll wanna kill yourself.] Anyway, you may need to experiment a bit to figure out what works. I also wanna say that it sounds like your heart is into it, but....Is your head? You need to be proactive everyday and take time, either when you wake up or while in the shower or something, to remember what you're fighting for and what kind of strength it will take. I'm not even kidding, make it part of your schedule [you should have a daily schedule of sorts]. You need to talk it into yourself, studies show that kind of thinking, along with positive ideas about how you CAN change, will make all the difference. Then make a schedule of tasks to do each day so you can have structure in your life, since its hard to know what to do with all that time when unemployed. Cold call places you find interesting, write cover letters, write thank you notes, work on interview skills, do something that enriches you, then work on your relationship [may need to buy a relationship help book too haha]. Maybe spend one of those days finding a part-timer to hold you over. Want fries with that? [Hey as long as you get a paycheck]. If you show her in your daily behavior, not behavior over stilted periods of time [like once a week or something lame like that], that your making changes like this, she'll be impressed. It shows motivation and initiative, and quite frankly.....If you dont try to change everyday like this, you won't make much progress. You'll be more likely to fall back into old habits and forget what you were fighting for in the first place, and thats when you'll get in big trouble, especially with her. Thats when you guys will get into a fight cause she'll see you doing the same things over and over with like, maybe one legitimate attempt at change a week. Don't give her a leg to stand on. But really, its not about her. It's unhealthy for you to think of changing in terms of whether or not you get to keep your girlfriend. This is really all about making you a better person. You are going against tough odds, my dear.
I really tried not to talk to you like you were him but I don't think I succeeded, haha I'm really sorry! I hope this helped.
Don't disappoint her