What quotes can help a person to deal with others negativity or obstuction of good?

I would like to have some great quotes for a group of people who want to go forward & do positive things..They want to help people who are gong through tough times..so it is a hard job helping people rebuild there lives from nothing..to have others obstucting their progress is the hardest part they have to deal with...so I want quotes that will help these positive people understand the negative ones & quotes that can help them overcome these problems so they can move forward & keep progressing.