There's a bit of a gray area in that optimizing time and attention management itself takes time and attention, and so your happiness and accomplishment aren't necessarily optimal in absolute terms after taking the time to work out optimal allocations. But that's a quibble; people very frequently engage in behavior they know at the time to be long-term suboptimal, and when we talk about things like willpower and akrasia we're primarily concerned with minimizing that sort of behavior.

With this in mind, I'd describe willpower as the component of your priority-evaluation algorithm that counteracts present-biased preferences. Hypothetically perfect willpower would mean no temporal discounting, although discounting future possibilities in proportion to probability of occurrence doesn't seem like a failure of willpower to me.