Few things can make us more miserable and negative than holding on to grudges against people. The reality is that we live in a world filled with imperfect people so it's inevitable that we will get offended and hurt by others from time to time. We can't avoid getting hurt in life but we can decide how we will act when it happens. We don't have to carry around our hurt feelings and let them grow into resentment toward others.
The best thing we can do to avoid holding grudges is learning to voice our hurt when it happens. If we can express how we feel to the person who offended us chances are high that the person will apologise, but even if we don't get an apology we will have voiced how we feel which makes all the difference. When we put our feelings into words we won't have to carry the negative feelings around with us any longer.