Chess is an interesting example. If you want to get good at blitz, playing 1min games over and over is a terrible way to do it in my experience. Playing 3hr games and studying theory is painful and annoying yet way more useful for real improvement. I think the same concept applies to many things - learning an instrument is another example. Performing a piano piece at full speed over and over is fun, but focusing exclusively on the hard parts one hand at a time slowly is far more useful.