Why often we fail to understand one's mind?

Every thought we think creates an impression in our mind, called ‘samskara’, the sum total of which forms our character. Change is the nature of mind, and it changes every moment. New thoughts and new character are created every moment. So, to read a mind based on a generalized character is a difficult task. However, if you are too perceptive to hear the gentle footsteps of their thoughts, you may win the game. 

Yes. Its true. we often fail to understand one's mind eventhough how close they are. Many times the reason may be we fail to speak openly about our inner feelings and we want others to understand what we feel and act according to that. This leads to misunderstanding. So, if we openly say whatever we feel about a person and solve the problem immediately there wont be any misunderstanding i think. But its tough to implement. Nothing is impossible. So lets try.

Mind is difficult to understand, even we fail to predict how our own child will behave in a particular situation. Over the years we may predict the behavior of our parents, siblings, or spouse, but we may not be 100% correct always. Hence, we should leave room for some surprises, this how humans operate.

Human mind is constantly evolving and hanging in its behavior, so let alone others even the person gets surprised at his or her reactions at times to certain situations in life...It is best to deal with orhers on a one to one basis rather than try and anlyse all their actions and deeds 

We are dealing the other person with our own thoughts in mind about them. We are not giving much patience to listen what they are coming to say. We are interfering in their speech and not understand it fully.That's why we cannot understand one's mind thoughts.

We fail to read our own mind properly and you're talking about others' mind. It's never easy to know what others have in their mind and concealing the expression is really so easy in doing so.

Human brain is complex and perplexing. It takes lot ofefforts to understand or peepthrough it. It's not uncommon some times not to understand our own brains.What to talk of other's brains.

If we have blind trust on the person than also we fail to understand one's mind

Face is not perfect index of one's mind. Only a person knows what is in mind. Normally, it is not possible to judge what goes in soe body's mind. If you could, any bad thins could bes stopped. For example, nobody could commit suicide if his mind could be read beforehand. . 

we fails to understand one's mind beacuse we all have different levels of observations, perceptions, maturity and understandings

This is because we don't want to understand others. Otherwise its not that difficult for us to know what other's having in their mind.

That happens because we fail to put ourselves in others' shoes and think from their perspective. Empathy, which means understanding how exactly others feel, is something that is generally missing. If we were to be more empathetic, then we would understand others better and our relationships with everyone would be far better.

We can know about other's mind when they are close to us. But knowing their mind 100% is not possible. Often people don't able to understand their own mind.