Kevin Archbold from Key Consulting shared a really useful distinction during his recent GiveGetWin class.
He does a lot of high level project management consulting and training, and his templates (linked above) are very useful for project planning.
One thing to look at is risks. That's a point where a project could fail or go off-track. By identifying these risks, you can plan in advance so they don't happen.
But Kevin made an interesting distinction -- the difference between a risk and a challenge.
His example --
Risk: "If the client is unavailable during this key point, we won't be able to move ahead."
Challenge: "The client is known to communicate poorly."
It's subtle, but useful to think through. A risk is something that could happen, that you'll look to prevent if possible, or have contingencies in place. A challenge is something that is already the case that you'll have to deal with.