This article from HBR gets a little life-hacky for my comfort, but I thought this bit was smart:
Phase 1: When we really have clarity of purpose, it leads to success.
Phase 2: When we have success, it leads to more options and opportunities.
Phase 3: When we have increased options and opportunities, it leads to diffused efforts.
Phase 4: Diffused efforts undermine the very clarity that led to our success in the first place.