I would add that many "deadlines" are actually just arbitrary project management bullshit that exist to create a sense of "urgency" because the people that make the promises to customers don't trust the people that do the work.

But on an individual level, procrastination and slipping deadlines has a deep seated psychological basis. The best way an individual can deal with this problem is by addressing internal motivations and their own emotional state-- that's definitely NOT in the PM-BOK. (see https://www.nytimes.com/2019/03/25/smarter-living/why-you-pr...)