Rav Nosson Zvi Finkel, the Alter of Slabodka

In doing a mitzvah, R’ Nosson Zvi taught, one must be careful not to cause unpleasantness or harm to anyone to avoid forfeiting its rewards.
He never gave shmuses during mealtimes.
When he prayed with a minyan, either he finished Shemoneh Esreh with everyone, or he knocked on his shtender to indicate that he congregation should not wait for him.

From Sparks of Mussar by R Chaim Ephraim Zaitchik