Learn to delegate/outsource at all levels from technical to mathematical: the best kind of delegation is to tools/systems/languages/type-systems (eg. "outsource your attention to the type-system") since it's always cheap enough to be in-budget...
Because otherwise you are solving problems someone else can solve just as easily. It doesn't mean be lazy, it means be selective about what you choose to do yourself. Its a big one in the seven habits book: Do, Plan, Delegate, Eliminate.