Question

“Do not devise harm against your neighbor while he dwells securely with you.”
The Sages inferred from this that one should not stay with a woman he intends to divorce.
Does this mean, as a general rule, that a person should not hide from others what is in his heart?
I’ve been renting an apartment for three years and I’ve decided to leave.
I’ve become very close with the landlord couple.
For various reasons, I know that the moment I tell him I’ve decided, an exhausting pressure campaign will begin,
and the relationship will also be damaged.
I want to tell him only according to the contract, meaning two months before the stated date,
but he talks with me warmly and happily, and the relationship keeps getting closer.
I heard from a rabbi that this is a problem.
Obviously there’s something distasteful about it, etc., etc.
The question is whether this is only an extra measure of piety, or whether it’s really something one is required to do.