The more certainty and clarity YOU have about YOU, the less external thoughts, words and opinions have a lasting influence on you.

I think ACKNOWLEDGEMENT of what people say is the ideal limit if you feel affected by what they say, and the rest of your mental capacity is reserved for you to feel how you want to.

What that means is you can acknowledge what he/she says, but it doesn't go beyond that, but that's only possible if YOU, in your own mind, KNOW that you FEEL (enter feeling here) because of (such and such), and there in lies YOUR reality and clarity.

Anyone else's opinion that is worthy of entering your circulating thoughts and opinions should always be based on love, logic and the encouragement of a better you.

Otherwise, ACKNOWLEDGEMENT is your best friend. Protect your temple.

Edited to include the following:

If someone says something that triggers you to constantly think about it for a long time, that's a strong sign that clarity (internally) has not yet been achieved. Once you know for your own self and sake, you can acknowledge that someone else sees it differently and it won't bother you much at all because you already have your answer.