I've been playing drums for about 4 years now. I've had my double-bass pedal for a little over 3 years. And I still absolutely suck at it. Two years ago I played Fade to Black - Metallica at my local music school. That song has some fairly fast double-bass parts in the outro. At the time, I could play them, so I was confident that I could improve myself even more very easily. Well, it turns out I can't. Last year was my first year at university, and since my drum kit was at my parents', I could practice much. Moreover, I stopped doing sports regularly; and what was even worse is that I overburdened my legs during field work for my study. So now I can't even play the double-bass parts in Fade to Black anymore, even though I could do it 2 years ago. Lastly, my stick technique and speed has increased only slightly; but my double-bass technique and speed have gone completely to shit and I just can't seem to get any better at the moment.
/rant