How to keep deadlines?

M. asks: How to keep deadlines? I missed on my savings plan due to market going down.

Problem Nr.1: Can't plan on markets short term. Market is it's own beast and does what it wants. See my post here. 

Problem Nr.2: The planning might be too tight. 

While planning, many people put themselves into a very tight time frame without leaving any room for unexpected and find themselves missing deadlines. 

Why does it happen? Why do people squeeze themselves into such tight deadlines? It appears to be a certain recipe for a failure... 
The reason may be the misinterpreting of the consequences.

I will explain it on an example. 

My friend had an appointment in a neighbour city which was 30 min away. We were in a car driving on the interstate. Without any bad traffic we still had at least 20 minutes to drive. But we were already late. He called the person he had the appointment with and said that he will be there in 10 minutes. 

I asked him why did he do that? Saying 10 minutes when we have at least 20 more. He said he didn't want the client to know that he will be that late. He planned to call the client again in another 10 minutes and tell him that it will be 10 more minutes.  And then hope that he will not have to call him again if instead of 10 minutes it will be longer. 

I told him that this would irritate me and that such a person would not appear reliable to me. 

He asked me what would I do not to anger the client. I said that I would apologize first. If I know that I will be 20 minutes late, I will tell that I will be 25-30 minutes late. That is to give me some room for the unexpected and not to have call several times. 
Every time you call and add more time to your delay is a separate disappointment. If you call 2 times, the client will be disappointed twice, if you have to all three times, he will be disappointed three times. And when you finally appear late, he will be disappointed that you are late. 
That is not a good start for a meeting. 

You give the waiting person small bits of time each of 10 minutes long and he can't do anything useful in that time. 
I would give him one bigger chunk of time of 25-30 minutes and that is enough to be used for something productive. I would prefer that for myself. 

In addition, if you manage to come a bit earlier, your customer will not feel that you are that late because you re-negotiated the time. After the changed time and changed  expectations, you are still late but that is a much better start for a meeting. Do you feel the difference?

My friend's perceived consequences were that he will disappoint the client less if he will falsely keep his hopes up.
The real consequences are: the client feels like waisting time and you appear as unreliable person.


My strategy

When making a budget for something (expenses or budgeting time required for a task) I over plan. 
If I estimate that I need 3 weeks for finishing up a project, I will say that I will need 4 weeks. I don't try to impress anyone with how fast I could work. The emphasis is on "could". Yes, I could, but that will be high intensity working and there will be no room for anything unexpected that can produce a serious distraction. 
At the end I will be exhausted with work and worries that I might not be on time (which equals to bad time management and unreliability). On the other side, if I have more time for working with good time margin for unexpected interruptions, additional checks or improvements, if I am done before the dead line that will be just a bonus for the receiving site in additional impression of competence, good time management and reliability. 

If I am doing something for myself, I plan the same way. If I want to be done with cooking in 20 minutes, I tell my husband 30 minutes. There can be many distractions at home: a cat asking for ham or ice cream or a child with something unexpected, or a phone call. If there are no interruptions, I can always use some free time for myself. 

My husband lives on a different time scale. He always underestimates the necessary time. I figured out the correction factor and now it works just fine. If he says that he needs 30 minutes, it means in reality 90 minutes. If he says 1 hour, that is usually 3 hours. That way I know, that If he plans us to leave the house in 15 minutes, I have time (about 45 minutes) to cook dinner or bake a pie.

What are the reasons for such behaviour pattern? 
I think that again it is the misunderstanding of the consequences, just like in the first example. 

By giving shorter times the person tries to present the situation better than it is. Then inevitably the truth hits strong and produces disappointment. 
Those people tend to hide the unpleasant facts even from themselves but with the effect of feeling more like a failure at the end. They see others being disappointed by them or they are disappointed by themselves. 

In case they don't feel like a failure and actually just don't care if they are late (like some who are habitually late), those people are just not worried about the consequences. 

Those people will not be late to the airport but they will be late to a restaurant dinner with friends. They estimate the consequences of being late for dinner as not important. 

And that just how their friends may feel: not important. In this case the reason is the same: the misinterpreting of the consequences. 
Is it really your intent to show your friend that they are not important enough for you to at least try to be on time? People like to feel important. Why not to give them that, especially if it is so easy. People always remember how you make them feel.