Having been a long time follower of Lifehacker, 43folders, Zen Habits, Pavlina and read the popular books (7 habits, GTD, etc), I can attest that 99% of people who study these end up just wasting all their time managing folders and todo lists instead of doing what's ON the todo lists.
What helped skyrocket my productivity was a paradigm shift in my thinking about work, and especially about others.
Little by little. Always. Don't work more than you planned to beforehand, even if you can or want to. Don't forget breaks and days where you relax. You need to get started, and if the task is overwhelming, not broken up into tiny 5-10 minute tasks, you just won't start.
This was a huge epiphany to me: Things don't get done if you don't work on them. No matter how much you plan, get hyped, talk and dream about, you have to actually 'do' - put in the effort. It sounds obvious, and it is, but I've never met anyone offline who actually does this. Everyone just talks.
This was also big for me. I used to spend a lot of time going on forums and asking the same question as you, and reading productivity blogs and so forth, because I thought that there was something wrong with me. I thought I was lazy, or had some mental illness preventing me from doing work.
But after years, I started noticing that the common man doesn't do shit. Who wants to spend their free time actually doing work? No one. Like I said before, everyone just talks, and you might be shocked at this, but when I was flipping burgers, there were people with Master's degrees working in the same position as me. WHY? Because they kept putting finding a new job off. "Once you get comfortable, it's hard to break the cycle you know" is what they'd tell me.
This was an epiphany to me, because now, instead of thinking I had a problem, I realized that working hard is OPTIONAL. It's my choice. 99% of people won't do it, and if I *choose* to be above these people, and with the 1% who are successful, productive, whatever (just throwing #s around, you know what I mean), then I had to "choose" to work.
Suddenly, work wasn't that difficult, because I would either do something, or say fuck it: "OK, I can bask here in my laziness, or get this done. I can't stay in the middle, worrying about when/how I can start. Do I just remove this from my todo list or do it RIGHT NOW?"
You're in charge of your life, and you're responsible for everything you do. You 'choose' everything you do. Going to work, school, feeding your kids, etc, is all your choice. Nobody 'forces' you to do anything.
And it took me a decade, plenty of meds, books, therapists and pondering for me to realize that. And nobody is going to heed this advice until they've realized it on their own. Why? Because I didn't, and nobody I've ever told did.
Oh, and GTD is targeted at CEOs of fortune 500 companies. The system applies to everyone, but trust me, if you're not productive AT ALL, then this system is more than a headache to keep maintained. But it's excellent and I use it now. It just took me awhile to get adapted to it, and I was only able to utilize it after I became more productive.
You wanna be a do-er instead of a thinker? Do, instead of thinking. Don't worry about whether you should do this first or that first, or if you have other things you should be doing, or waiting for 'the right time' to start, or about things going wrong. Just do, make it a Zen experience.
Read Zen and the Art of Motorcycle Maintenance. Excellent book! Along with Power of Now.