You have to allow time for interruptions, distractions and emergencies. Expect the unexpected. I get this all the time working at a health club. I'll be sitting in my office working on a project and all of a sudden in pops a client. "Hey Tim, can you give me a spot?" or "I'm not sure how I should be doing this exercise, can you give me a hand?" This happens all the time. To be truthful, I don't mind it. After all, my job is to help people, however difficult it becomes to complete my office work.
I'm sure a similar situation like this has happened to you whether you are at work or in the home. It's important that we plan our day knowing that we will be interrupted. Time management experts say that you should plan to use only 50% of your time. Therefore, when you get distracted, you will still have time to accomplish the important things.