Hi,
@Piotr. Don't feel bad. I struggle with the same thing you do. I've recently had some insights that have helped me and I'm happy to share them on the chance they may be useful to you or anyone else.
To provide some context (no pun intended), my life's dream has been to work as a professional comic-book writer and illustrator. But a long time ago I allowed myself to become convinced that this was not realistic or worthwhile to pursue (how that happened is beyond the scope of this conversation). So I tried to content myself with a "normal" career, but at the age of 49 I've realized that I've lived every day yearning for something else and I'm not happy with the life I've created. I believe it was a mistake not to pursue this goal. If I don't at least try to achieve it, I know that when I reach the end of my life it will be with a terrible regret. (There is no guarantee of success, of course. I can live with that. But I can't live with never having tried.)
I've tried a number of GTD-centric solutions. I recorded a 3-to-5 year goal of becoming a comic-book professional. I've tried time-blocking as
@Longstreet advocates. Tried creating new contexts. Tried restating my projects and next actions related to this goal. Nothing helped. At the end of every day I'd go to bed having neither written nor drawn anything.
In the last few weeks it dawned on me: the problem wasn't with my lists or my GTD system. That's because there's no magic to GTD. Your GTD system is nothing more than a reflection of your own thoughts. And I was laboring under the mistaken belief that I had to get everything else done on my plate before earning the right to spend some time pursuing my life's ambition.
I now know that the only way to bring this dream to fruition is to spend some time every day writing and drawing, and if other things have to fall by the wayside, so be it. Because I'm a morning person, every day before work I spend 30 minutes writing and 30 minutes practicing drawing. I tackle other things later. (If I were an afternoon or an evening person, I'd structure my day differently. But I trust you get the point.)
My GTD lists now look different to me, because I have an understanding of what's truly a priority in my life.
Perhaps it might be worthwhile to look at your own priorities. Are the things you're not getting done important to you? Perhaps more important than the other things you're getting done on a daily basis? Then you might want to make some different decisions about what commitments you're making in order to allow time for what's important. Conversely, if these things you're not getting done aren't important you may want to let go of them and stop beating yourself up.
Others have already done a good job suggesting some GTD techniques to help pare down your lists, and I don't think I have much to add there. I think they're all potentially useful suggestions. In my case, though, I had to get clear about what I wanted out of life before any life management techniques could be helpful.