Purposeful practice, after Ericsson and Pool requires that you’re always pushing your comfort zone. By honing a given set of practices, it’s often possible to perform incrementally better, but returns usually diminish. At that point, “generally the solution is not ‘try harder’ but rather ‘try differently’” (Ericsson & Pool, 2016, p. 19). (Compare to Naive approaches to practice rapidly plateau)
Consequently: Practice efficacy is highly sensitive to method design.
Coaches can help here, since they’re generally familiar with the barriers you might encounter, and what alternative approaches might help.
Nicely summarized by “What got you here won’t get you there.” (Marshall Goldsmith).
Chase, W. G., & Ericsson, A. (1981). Skilled memory. In A. Ericsson (Ed.), Cognitive skills and their acquisition (pp. 141–189). Erlbaum. https://apps.dtic.mil/dtic/tr/fulltext/u2/a114635.pdf
Ericsson, A., & Pool, R. (2016). Peak: Secrets from the New Science of Expertise (1 edition). Eamon Dolan/Houghton Mifflin Harcourt. Peak - Ericsson and Pool