Trying to get a handle on this now. So nowhere near perfect, but getting there.
I set huge driving lifelong goals. (Financial independence, Be a good husband/dad, fitness etc...)
Then I work backwards to yearly, monthly, weekly & daily goals. What am I doing in the short term to work toward the long term?
I compare the crap I actually have to do vs my goals. Am I working towards something or just working? Is something important to me not on the list of goals?
Then I try to rearrange my to do list so that the "mission critical" stuff gets done first. Calling it priorities makes them seem preplanned and rational, it's more like triage.
This practice is helping me decide what's compelling and worth doing. But I'm in the baby step portion of all this.