Answered by Sayyidi Habib Umar bin Hafiz (may Allah protect him and benefit us by him)
When I give someone sincere advice (nasihah) and they reject it I become upset. How can I tell that I am upset for Allah’s sake and not merely because that person has gone against my will?
If you are upset by someone not accepting nasihah given by anyone on the face of the earth then you are sincere, but this should not cause you to become angry or harsh. If you are upset only when someone does not accept your nasihah, then this is a sign of a lack of sincerity. In any case you should be suspicious of your own motives, while continuing to give nasihah, motivated by an immense concern for others. You should ask Allah to guide you and all His slaves. You should look at how well you accept nasihah from others and how happy you are when someone gives you nasihah.
What is the best way to accept nasihah?
Be glad that you have received it and reflect on how to apply it and benefit from it as much as possible. Thank and pray for the person that gave you it.