From the book Make It Stick: The science of successful learning (Brown, Rodiger, and McDaniel, 2014), interleaving your practice (mix it up, and be okay with ea

From the book Make It Stick: The science of successful learning (Brown, Rodiger, and McDaniel, 2014), interleaving your practice (mix it up, and be okay with each subject feeling difficult), and using active recall (for example, before looking something up, commit a guess and risk being wrong) seem to be effective in general. Only throwing fastballs until comfortable, and then switching to knuckleballs, might feel easier but tends to result in slower skill-building.