Encouraging the Good and Forbidding the Evil.
Remember to have good intentions. You don't want to make your brother/sister feel bad and you're not trying to make them feel inferior. Rather you just want whats best for them in this life in the next, and you want to help them. Remember the word Naseehah (Sincere Advice). Use wisdom and try to advise privately, or take to the side, instead of announcing their problem publically and pointing them out (with regard to good-hearted mistakes).
True zuhd is not caring about people's opinion with regard to you as long as you are doing things correctly the way that Allah (Swt) wants you to without trangressing any limits within yourself or physically. Whether people praise you or dispraise you is the same as long as you are doing a deed correctly that is most pleasing to Allah (swt) without over stepping the bounds.
And Allah (Swt) knows best.
Oh Allah please Forgive us and Purify our hearts from all evil.
Oh Allah please protect our hearts from arrogance and sickness. Indeed You are The Best of Protectors.