Perhaps this is because it is very easy for us to spend more time developing our capabilities than we spend actually using them. Certainly you want to be capable and effective, but take care not to become a slave to mere capabilities. Don't put so much time and effort into being able to do something that there's no time or energy remaining to actually do it.
Preparation is vital.
Yet at some point the preparation needs to end so the actual doing can begin. Being highly prepared means very little if nothing is ever attempted. Learn by doing, not at the expense of doing. Rather than collecting empty, unused capabilities, develop your capabilities in response to the challenges you undertake. Sure, it's enticing to be able to send e-mail while walking the dog.