Where would you go if you had six months to travel? Would you be aggressive and do as much as possible? Or take it easy? This is the conundrum that you face in creating an achievable and fun trip.
There are so many options to consider when you plan to go around the world. We originally had the idea that we would use an "around the world" ticket, and thus were constrained to 1) go one direction, and 2) only visit a limited number of locations.
For better or worse we stuck with that approach even after we realized there was literally no way we could plan the entire trip up front, with no latitude for changes. Fortunately that is not our style. Unfortunately it means that there is a ton of legwork once you frame your trip that you must do. How can you get to Bhutan from Tokyo (spoiler: you can't)? Where will friends and family meet you during the trip? How much flexibility do you / they need?
For our adventure, we time-boxed it and decided to only visit places we had yet to see.
Even with this decided, the details create challenges.
Prioritize the big pieces
We can't try to micro-plan everything. We'll make sure we have a macro-schedule and make the pieces fit together.