This may be way out in left field, but I seem to sense that this falling back and procrastination might be stemming from, not your goals and desires, but the source from where they come from. The goal might be very motivating and fill you with passion, but I think something deeper is telling you that they aren't quite right for you, or maybe even though they are right, but right for a different reason.
I think this reason could be your values. You know what you want out of life, and you know your goals, but do you know what is most dear and important to you? I think the methods of reaching your goals is stepping over something even more important to your fundamental self and this is causing you to hesitate. In fact the direct line was this one:
I've got a family that's living on scraps but is still financing my living here.
If this sounds like it could be a source of your issue then the next step is to discover and explore your values. If you still have access to 7 Effective Habits, then this is habit number 2, writing the mission statement for your life. It goes through the steps for finding what's important to you, and creating it into a statement that reflects your deepest values. This statement then can be used to refocus your goals and aims so that what you are working on becomes aligned with what's most important. When this happens the procrastination problem will fade as the conflicted feeling within vanishes, if it's a matter of values and not discipline.
The article of Steve's that would help the most would probably be How to discover your life purpose in about 20 minutes
closely followed by Motivation for Smart People
I think you were spot on when you said it's something deeper, something at the core. Just keep looking, exploring and writing down what you find.