In my (vast, sorry to say) experience, procrastination is the direct effect of not having manageable goals.
But , with Japanese, I've been doing really well since about November of last year. It's been a nice experience, hopefully I can use what I learned for other things as well. (I believe that by JaLUp standards, I've been power leveling, for most of this time - I slowed down lately, but on purpose - I find that it's no longer necessary to power level, I'm happy with a slower progress because I can already enjoy a lot of things in Japanese).
How have I been able to do so well? I set a reasonable daily goal for myself (right now, I'm only doing SRS-ing 4 hours a day, and that includes adding new cards, and sometimes I even cheat and include time spent reading), and then do the reviews right as I wake up (I do timeboxes, but 25-30 minute timeboxes with only short breaks in between them). This way, I spend most of the day happily going about my business, instead of thinking about having to do reviews. More importantly, I also set a reasonable goal as far as the chunk of work I'm planning on getting done, over time. For most people, "I'm gonna finish Core6k" is not such a reasonable goal. If you haven't toiled away at the same task for 200+ days, all by yourself before, then setting such a massive goal now, with this, is just setting yourself up for failure.
If you aren't progressing with Core6k at a fast rate, you really, really should consider changing your goals. Instead of Core6k, set it as a goal to do 500 or 1000 Core cards (frankly, 500 sounds like the best idea, for now), and then move on to something else (grammar sentences, maybe later decide to do another 500 core sentences, if you want). With 500 cards, you can set up a deadline that's close enough to give you the motivation you need. With 6000, you can't.
I'm not doing Core6k (nor am I using subs2srs) anymore , I'm making my own cards. I only did about 1000 Core cards, and another 700 Tae Kim sentences. Both of those I went through quickly, because they were manageable portions (smaller portions than RtK, which I had already completed in six weeks, so I knew I could do these faster that that). And, since I knew I was only doing 1000, it allowed me to be selective over WHICH 1000 I did. I was suspending new cards left and right, because I had plenty to choose from. That helped too.
As for what to do next, (production) cards you create yourself are far more enjoyable than pre-made decks. Right now, that's what I'm doing. I pick the words from reading materials, and then look up example sentences on Yahoo, but I don't have anything against subs2srs, you can try that too. I don't have a fixed goal as to how many cards I plan on doing, instead I'm going day-to-day, on this 3-4 hour schedule. But I do have a goal, to gradually reduce the amount of SRS-ing as I progress with being able to read. In two months, I won't still be doing 4 hours of SRSing a day. The fact that this schedule is limited in time keeps me motivated. Without it (if for instance I was planning to do this for 6 months or more, to the effect of thousands of cards), I seriously doubt I could actually be doing 4 hours/day even for the first week. I know myself, and I know that I need small goals or I'm lost.
It's better to do 4 hours/day for a single month, than not do anything but act like you're trying to, for 6 months or a year. And, contrary to popular belief, working from dusk till dawn is in fact not the key to personal success.
Edited: 2013-03-18, 9:49 pm