I've always been a morning planner by default and wondered if planning in the evening is any better so I tried it out for a few days. The big surprise so far is that my mind works more effectively with a whole night to digest the next day's plan.
I feel calmer moving through meetings and work. I think this happens because I've subconsciously rehearsed how the day will play out. It's the same as the mental walkthrough that you'd do the night before a big trip to make sure you get out the door, into the cab, and to the airport with time to spare. Once the day comes, you can stay in a flow state of execution since you've already made decisions. I wasn't expecting this strategy to make normal work days feel calmer too.
If my plan for the next day includes creative or intellectually satisfying work, I feel more excited than usual to work on it. Once the mind is trained on a problem, it gets to work and starts generating ideas and solutions in the background. An entire night of subconsciously solving a problem builds up a kind of potential energy that feels ready to burst into something tangible. I think there are limits to this. I find that a weekend is usually enough time for this mental potential to build up and dissipate. But perhaps that's because my stimuli on weekends is varied and orthogonal to my work unlike weekdays which are ruthlessly uniform.
I am also not great at unplugging mentally or emotionally from work. And working from home doesn't help. Planning out the next day acts a separator and gives me permission to end the current workday which makes the evening feel more restorative.
I only found two compelling reasons to avoid evening planning. If your priorities can change abruptly because of a work or message you get overnight, then planning the night of can feel like wasted effort. And if you end your days feeling drained, you'll make dull decisions about what's important.
Since I need to be responsive to colleagues and customers, I've adopted a hybrid approach. I plan out my day in the evening and finalize it in the morning to account for changes.