We're not designed to preemptively multitask; I just crash my stack when I try. We can cooperatively multitask, but the context-switching has to planned ahead. Even then, interrupts are costly. Used to be there was nothing between me and putting in a sleepless weekend on a project except me and my fatigue, which enthusiasm overcame easily. Now I've got kids and elderly parents and they're not only interrupting, they're nonmaskable. Stack-crash, context-dump and a profound weariness from loss of momentum, next stop.
I love it when I can shove in the earplugs, unplug the phone and dive in on a new learning adventure -- I hunger for that, it's part of who I am. Those times when I can trust the world to handshake timeslices and mask interrupts are very rare these days, however. From the outside it might look like slower learning; from in here, it's that the learning seldom gets any runtime.