This is good advice, but I struggle to apply it when many people are involved in a project.
If proceeding requires a review/input from someone, its a difficult balance between respecting their busy workload may mean they only get to it next week, or letting momentum die.
Yep, this is the hardest part. Big groups slow everything down. I have found it helps to keep moving on what you can control while you wait on others, so you don't fully lose the thread.