It's easy to get caught in this habit. Everyone feels busy, you have to "get stuff done" but you don't have time to think about how long that "stuff" will take. Then when we work with others we have no idea how long tasks with them will take also. So both people's schedules are now being run by the seat of your pants.
Surprise somebody the next time you need a little bit of their time. Take a few minutes to think about how long it will take. If you are not totally sure, tell them how much time you estimate it will be. Try using an uneven or uncommon time amount. "Can I get 7 minutes of your time?" That will surprise them, maybe make them laugh, but if you have thought out how long it will actually take, you might be close!