To forgive from the heart is just an expression that means forgive from a place of love. Don't begrudgingly forgive someone, that means nothing. Forgive someone from the goodness and kindness in yourself, and in doing so you release the unforgiveness and hate.
forgive and you will be forgiven of all your sin. forgiveness is not easy its a process, and always look at Christ who died on the cross who without sin dies for us.
