What is closeness? 

When somebody is very close to you, and somehow they know all about you. In fact, you are the only one who is sharing all the personal things and problems that you are suffering from.

But if you forget to tell them, then what will happen, imagine...they feel irritating. They will think in their free time why you hide it from them. They can’t stop themselves to ask why you did this.

Or another situation,

You don’t want to tell them, you want to keep it private. And somehow they know about it what you try to hide it.

They started disliking you. They think and decide not share with you again and they prepared their mind for small revenge.

But at last, why you don’t want to share it to your close person.

When some close person knows about you, they have a curiosity to know about you more and more and also pre-assumption is that not to hide it from them. And may be, you have fear that they will make it gossip, they tell it to everyone.

And another reason is, they give you advice. The first time, you gonna love that advises. The second time, you also gonna love it. The third time, you like it. And one more time, you feel bored and you think that you are not so stupid to handle your problems.