The following quotes by Srila Prabhupada illustrate the principle that "Forgiveness is Not Optional in Our Spiritual Lives."

A Vindictive Mentality Will Spoil One's Krsna Consciouisness

The word titiksava, or "tolerance," indicates that a transcendentalist must be forgiving. The material world is full of embarrassing and irritating situations, and unless one is inclined to be very much forgiving he will become infected by a vindictive mentality, which spoils one's spiritual consciousness.

(The definition of vindictive is: revengeful in spirit; inclined to seek vengeance)

Without Tolerance We Cannot Be Successful

"One should chant the holy name of the Lord in a humble state of mind, thinking oneself lower than the straw in the street; one should be more tolerant than a tree, devoid of all sense of false prestige and should be ready to offer all respectto others. In such a state of mind one can chant the holy name of the Lord constantly."

We must always remember this verse and be as tolerant as the tree, as we execute the Krsna consciousness movement Without this mentality we cannot be successful.

(Sometimes ksama is translated as tolerance and sometimes forgiveness)                                                                               Forgiveness is the Real Feature of Austerity

A sadhu, a devotee, is never angry. Actually the real feature of devotees who undergo tapasya, austerity, is forgiveness

The First Duty of the Tapasvis is to Forgive

Tapasvi, those who are advancing in Krsna consciousness, undergoing tapasya, austerities, their first qualification is to forgive the offender. This is the qualification.

Those who are tapasvis, their first duty is how much he is forgiving. How much he has learned to forgive.

Forgiveness is the Special Quality of the Brahmanas

Brahmanas are beautiful when they are forgiving, ksatriyas when they are heroic and never retreat from fighting, vaisyas when they enrich cultural activities and protect cows, and ciidras when they are faithful in the discharge of duties pleasing to their masters. Thus everyone becomes beautiful by his special qualities. And the special quality of the brahmanas, as described here, is forgiveness.

A Devotee Is Understanding

So a devotee is always very understanding if there is some discrepancy behavior on the part of nondevotees, and even some devotees misbehave, he is always very tolerant and understanding.

Krsna is Pleased With Those Who Forgive

The duty of a brahmana is to culture the quality of forgiveness, which is illuminating like the sun. The Supreme Personality of Godhead, Hari, is pleased with those who are forgiving.

The Lord is very satisfied with His devotee when the devotee greets other people with tolerance, mercy, friendship and equality.

Forgiveness is a Survival Tool

I am glad to learn that your co-operation for this society is appreciated by the authorities, We should learn to forget and forgive minor incidents because whenever there are two men in a place, there is always some misunderstanding.

Overlook Their Mistakes

"Even if a devotee commits the most abominable actions, he is to be considered saintly because he is properly situated,". As you will say, "To err is human", so in the neophyte stage we may always expect some discrepancies are there. Kindly see the things in this light and forgive their small mistakes. The big thing is they have given their life, everything to Krishna---that is never a mistake.

 

The Mind Is the Cause of Happiness and Distress

The brahmana said: These people are not the cause of my happiness and distress. Neither are the demigods, my own body, the planets, my past work, or time. Rather, it is the mind alone that causes happiness and distress and perpetuates the rotation of material life.  Failing to conquer this irrepressible enemy, the mind, whose urges are intolerable and who torments the heart, many people are completely bewildered an create useless quarrel with others. Thus they conclude that other people are either their friends, their enemies or parties indifferent to them  11.23.47

See Others Offenses as Our Karma

If someone bites his tongue with his own teeth, at whom can he become angry in his suffering?

We Suffer When We Inflict Pain

Suniti said to Prahlada. My dear son, don't wish for anything inauspicious for others. Anyone who inflicts pains upon others suffers himself from that pain

Resentment is a Symptom of Ignorance      

Anger and resentment are due to ignorance due to material attachment. We have to solve the problem through knowledge and purification.

Other Pertinent Quotes on Forgiveness