Sometimes things are better left unsaid

I read this post on a forum which I joined.
This guy has a secret which he dont want to tell to his current gf.
What the secret is, I don't know and I don't care to know.
He just ask us (readers) whether or not he should tell his gf before he is married.
It was a part of his life in the past and he was scared if his gf knows, she might not want to marry him.
In the other side, he thought that before they get married his gf should know everything about him, he should be totally honest to her.

People told him that he should think, whether or not his gf will ask about this.
and he said no.

Then people told him that somethings are better left unsaid.
If u don't tell, it won't cause any hard to anyone.
But if u tell, it might cause harm to the relationship.
So what's the point of telling her ?

Furthermore, people told him if not telling the secret to his gf bothering his mind, then he should just tell her with all the consequences.

I personally think that I agree, sometimes, some things are better left un said.
Not saying anything doesn't mean u're lying.
Lying is when the fact is A and u said B.

Well, for me sometimes I don't want to know so much.
I don't care so much
and I wish I just don't know as much
Because by knowing it will bothering my mind
it will break my heart
and I will be fine if I don't know.