Honing the art of perfect 'doing': smart, suave and marketable

Need to learn the art of balanced "doing". But fall off the rope usually. Most of the time it's underdone, and the consequent target misses, falling off the mark, and more importantly the rumbling shadow of self doubt, reproach, frustration, helplessness and even cynicism. Other times, it's overdone, and its precipitous after effects, falling off the cliff with the overdrive, giving more despair than not doing at all, and resultant efforts to undo, to chip down the extra, and getting into a zone totally crazy beyond the extremes of overdoing and underdoing, landing in a zone where you no longer know whether it's a tragedy or a comedy. God when will I learn the suave art of just doing, finely balanced, perfectly nailed, expertly nuanced?