I dont hold grudges anymore. A few years ago I had a fairly big confrontation with a friend of mine who I thought was doing something "wrong" but I realized that it was simply my opinion and I was judging him on what he was doing when the truth was simple, I created a meaning out of what he was doing and judged him.
I thought about it for a long time and the more I think about it the less it makes sense to hold a grudge, there is simply no point. These days for me it is quite easy to let things go and simply accept people for who they are...simply because thats who they are.
Also I learned that for me to let go and to move on, I need to forgive myself for having judged the other person or for having done something that caused harm to others.
There is no secret formula that works for everyone which will make it so you wont ever hold a grudge. For me the most effective tool I use to gain clarity about certain things is 'self-enquiry'.

