Friend, it is important to forgive.
We all have been hurt in some way. Many of us have been or are being abused. Hateful things are said about us when we know in our hearts that we have not done or said the thing we are accused of. I could go on and on, right?
The Lord asks us to forgive and so we must at the very least, begin to look into our own mind to see who we should forgive. It is impossible to fully forgive without the help of the Holy Spirit. Traces of our hurt will remain otherwise.
To receive forgiveness from the Lord and then to not forgive others - this cannot be a part of the Kingdom of God.
If Almighty God has forgiven you then you are required to forgive others and not hold onto grudges, or hate or be filled with anger or revengeful thinking towards another. We are human and we will be affected in this way but as soon as it appears we must deal with it in a Godly way.
We must go straight to the Cross, lay it all there and ask for the Lord's help. He will release the Holy Spirit to work with us to overcome, because this is the Way of Life.
Forgiveness, it is everything in a believer's life. Continual forgiveness, because He has forgiven us, past, present and future if we are repentant and genuine.
The Bible says "If we forgive those who sin against us" - which tells us that we will be sinned against. Over and over. There is none perfect, so we too will sin.
It's all about forgiveness and repentance. It's so healing to our body and spirit to receive forgiveness and to give it also.
Practise it often.