"If you’re not learning you’re standing still" This is a large understatement. In our industry, if you're not learning you are drifting backwards rapidly. I aim for twenty hours a week of (unpaid) reinvestment and learning. Some weeks I still feel like that's not enough to stay current. Does anyone else feel the same way?
Standing still as rotting is bad obviously, but to me, just seek things that provides a sense of eager. Be it walking, boxing.. "make it" passionating (as in seek what tickles that sense). If semiconductor physics does that, enjoy it. But the emotion is what motivates me now. I think it's more important to replenish that than learning. You'll learn later when you're fulfilled, and probably 10x times better and faster.